Obrazy na stronie

Deviation of Polarised Light by Solutions of Inverted Sugar. Clearance

May 16, 1879. tainty of gun-cotton in the earlier stages of history, | Bower), burning slack or small coal. In this way a coatnaturally gave rise to a persistent scepticism regarding its ing of 'magnetic oxide is formed close to the surface of presenting trustworthiness, appears now also about to the iron, but this is often slightly covered with red oxide, adopt wet gun-cutton for military and naval uses.

Fe2O3. The admission of air to the furnace is then so But while the usefulness and great value of compressed arranged by a suitable apparatus that a stream of carbonic gun-cotton in these important directions has been esta oxide is passed over the articles for a short time, and the blished, its technical application has made but slow red oxide very speedily reduced to magnetic oxide,– progress as compared with that of the simple nitro

3Fe2O3+CO=2Fe304+ CO2. glycerin preparation known as dynamite, which, in point of cost of production and convenience for general blasting reduction to magnetic oxide, is very readily detached from

It is worthy of note that although the red oxide, before purposes, can claim superiority over compressed guncotton. Already, in 1867, a number of dynamite factories, i the iron, after the redu&ion the Fe304 so formed is perworking under Nobel's supervision, existed in different featly, hard and homogeneous. From all appearances it countries; in that year the total quantity manufactured would seem as though a kind of fusion took place, but at

the same time it must be recollected that the temperature amounted to 11 tons; in another year the produce had risen to 78 tons; in 1872 it had attained to 1350 tons. used (a red-heat) is very low to favour such an adion. Two years afterwards the total production of dynamite

The oxide formed by this process has been tested very was nearly trebled, and in 1878 it amounted to 6140 tons. thoroughly, and withstands the ordinary oxidising infuThere are as many as fifteen factories in different parts

ences perfectly. of the world (including a very extensive one in Scotland) be dealt with by his processes, and will present opportu

Mr. Bower has several contra&s in hand which are to working under the supervision of Mr. Nobel, the origi- nities for the practical testing of the two processes from nator of the nitro-glycerin industry, and some six or seven other establishments exist where dynamite or preparations

a commercial point of view. of very similar character are also manufactured.

How far the rate of production of dynamite will be affected by the further development of the value of Nobel's

ON THE INFLUENCE OF new preparation, the blasting gelatin, it is difficult to foresee, but there appears great prospect of an important

VARIATIONS OF TEMPERATURE ON THE future for this very peculiar and interesting detonating


BY SOLUTIONS OF INVERTED SUGAR. It is hoped that the subjects dealt with in this discourse afford interesting illustration of the intimate connection

By P. CASAMAJOR. of scientific research with important practical achievements.-F. A. A.

The researches, of which I propose to give an account in this paper, were suggested by an interesting communica. tion of Dr. Ricketts to this Society, which was presented

at our last meeting. A NEW METHOD OF PRODUCING A COATING Dr. Ricketts found that the temperature at which the OF MAGNETIC OXIDE ON IRON SURFACES. deviation of a solution of inverted sugar becomes 0 is not

90° C., as given by some authors, but 92°, or rather 91•7°C. By GEORGE R. TWEEDIE.

From this Dr. Ricketts concluded that if a solution of

commercial sugar is inverted in the ordinary way, if It will be remembered that last May I had the pleasure originally the two constituents of the sugar were cane of laying before the readers of the CHEMICAL News a few sugar and inverted sugar, after inversion there must only details respecting Mr. Geo. Bower's process for producing remain inverted sugar, and if we bring this solution in a coating of magnetic oxide of iron by the adion of hot | the saccharometer tube to have the temperature of 92° C., air.

the indication of the saccharometer scale must be o. A continuation of the experiments has led to the pa. As the inversion of sugar solutions in testing sugars is tenting by Mr. Bower of a second process of considerable now almost entirely neglected, it struck me that the introinterest.

duction of this subject before this Society was of great It was ascertained, during the time the experiments importance, as it is likely to excite inquiry in this direc. with the air process were being carried out, that the tion, and must lead to interesting discussions which will magnetic oxide was formed by the oxygen of the air com. throw much light on a ground which has not recently been bining with the carbon of the iron and forming carbon di. explored. I hope the following remarks may be conoxide, which in presence of the heated iron was split up sidered as a contributiun to this important subject. according to the well-known reaction

To enable me to present in a clear light the results I 4CO2+ Fez=Fe3O4+4CO.

have reached, it becomes necessary to bring before you

some theoretical points relating to the inversion of sugar This fact readily explained why the process was unsuit

solutions. able for wrought-iron or steel.

It is to Mitscherlich that we owe the observation that It was then resolved to carry out a further series of experiments bearing on this fact, and the best means of polarised light varies with the temperature. It is, how

the deviating power of solutions of inverted sugar on applying it practically. Pure carbon dioxide prepared in ever, to Clerget that we owe a careful study of the subject. the usual way was first tried. A silvery coating of mag. As far back as 1849 he published in the Annales de netic oxide was formed after an exposure of about seven Physique et Chimie (vol. xxvi., 3rd series, p. 175) a process hours at a dull red-heat; the coating, however, was crys- for re&ifying errors in tests of commercial sugars by talline and somewhat brittle, although very hard. Very long and tedious sets of experiments were then tion caused by a solution of inverted sugar, obtained by

Soleil's saccharometer, by taking into account the devia. carried out with mixtures of carbon dioxide and air, air heating with hydrochloric acid a sugar solution, preand carbonic oxide, and varying exposures of the three viously tested without inversion. In this communication, together.

however, Clerget does not enter into theoretical considera. The following is the method of procedure now adopted, tions. He directs that sugar solutions shall be inverted and which answers most satisfactorily :-The articles are by heating them with 10 per cent of their volume of confirst of all heated, and acted on for a certain period by the centrated hydrochloric acid up to a temperature of 68° C., products of combustion largely mixed with air from a pe. culiarly constructed furnace (designed by Mr. Anthony * Read before the American Chemical Society, Feb. 6th, 1879.


Ĉ Hentet es, } Deviation of Potarised Light by Solutions of Inverted Sugar. 263 taking about ten minutes in the operation. As soon as slight, and as the impurities are in small quantities when this temperature is reached, the solution is to be cooled compared to the cane sugar, the changes they suffer may down to some temperature between 10° and 35° C., as the be neglected, and we may suppose that, with the exceptable he gives for correction is calculated for temperatures tion of the conversion of cane sugar into inverted sugar, between these limits, which, he says, "answer for all no change takes place in the other constituents of the occasions which may present themselves in “ Europe, as commercial sugar from the treatment with hydrochlorie well as in the Colonies."

acid. When Clerget proposed this new plan for making sugar After this action of hydrochloric acid, aided by heat, analysis more correct, the subject of testing sugars was has taken place, the solution is examined again in the not a new one with him, for it is to him that we owe the saccharometer, and, after making a deduâion for the idea of using Soleil's polarimeter as a special instrument volume of acid added, we will obtain a deviation, d. for analysing sugar, and, as far back as 1845. he had pub. This deviation in ordinary sugars will take place on the lished, in the Bulletin de la Societe d'Encouragement, an negative side of the scale. We may suppose that it is account of Soleil's saccharometer. In his paper in the the resultant of the same elements that made up deviaAnnales de Chimie et de Physique he gives no theoretical tion D, with the exception of the quantity C, now reprereasons for the new process. For the theory of the correc. sented by the deviation due to the inversion of the cane tion of the direct test of the saccharometer, by taking sugar originally present. This quantity we will call - 1, into account the test after inversion, I am indebted to and we shall have – I-ith-g=d. If now we wish some formulas in Mandlebluh's Guide (Leitfaden zur to eliminate the quantities i, h, and g, we may easily do Untersuchung der Verschiedenen Zuckerarten, Brunn, so by subtracting the second equation from the first, and 1867, p. 56). This theory I will now proceed to lay before we shall have C +1 = D - d. you.

By a series of experiments Clerget established the You are aware that commercial sugars contain, besides relation between C and the corresponding value of I. This pure cane sugar, a variety of substances, of which many relation varies with the temperature, but we may suppose exert deviating effects on a ray of polarised light. Among that the observation, after inversion, is taken at 28° C., at these is inverted sugar, which may be an immediate sub- which a quantity of cane sugar which, before inversion, stance or a mixture of dextrose and lævulose. This latter gives a deviation of 100 to the right, will show for the supposition was advanced by Dubrunfaut, but has never corresponding inverted sugar 30 to the left or - 30. At been demonstrated in a satisfactory manner, although it this temperature C + I becomes 1'3 x C = D.- d. As dis would take volumes to collect what has been written about a negative quantity the algebraic subtraction is equivalent it and is being written about it every day.

to an arithmetical addition, whence we draw the rule that The other bodies which accompany cane sugar have not at 28° C., the true quantity of sugar C is equal to the sum been studied in such a way as to throw light on their of the two deviations divided by 163, asnature, with the exception of aconitic acid, isolated by Dr. Behr, who gave an interesting account of his re


D-d searches in a paper read before the Society two years ago.

A point of great importance in connection with the This number 1'3 corresponds, as we have said, to 28°C. analysis of sugar by optical methods is that the impuri. We may in the next place inquire: What are the correties which are generally present are in such a condition that they seem to exert no effect on polarised light. The sponding

numbers for other degrees of temperature ? This proof of this is to be found in the fact that with most brings us to the consideration of Clerget's table. For sugars, particularly if the saccharometric test is above 9o these numbers, and on consulting his table we find that

temperatures between 10° and 35° C., Clerget determined per cent, the result

, after the correction for inversion, is for a quantity of cane sugar equal to 100 we must take for the same as given by the direct test. As many of the the quantity D-d at rooc., the sum 139, and that for impurities reduce the alkaline solution of tartrate of copper, they are comprised under the head of inactive every degree C. above 10°, up to 35°, the number repre

senting the arithmetical sum of the deviations is equal to glucose, concerning the nature of which there are many 139 minus one-half the difference between the number unsatisfactory doctrines. To explain how the direct test by the saccharometer have 20 - 10 = 10 and 139 – 10 = 134; for 28°, we have

representing the temperature and 10°. Thus for 20, we may be corrected by subsequently inverting the solution | 28 – 10 = 18 and 139 - = 130 ; for 35°, we have 35 on which this direct test was made, let us suppose that we have in the first instance a deviation, D. We may

10 = 25, and 139 – 28 = 126.5, &c.

If the same law should hold good below 10°, we must, suppose that this deviation is the resultant of the following :

to 139°, add $ for every degree below 10°, and this leads us

to establish that at oo, the number corresponding to + C, deviation due to the cane sugar.

D-d would be 139 + 5 = 144. As this number 144 is one inverted sugar.

of great importance, allow me to recall to your attention th

one or more substances, besides that it means that if we have a solution of pure sugar cane sugar, which turn the plane of polarisation to which will produce a deviation of 100 divisions on the the right.

positive side of the saccharometer scale, if this solution - 8, deviation due to one or more substances, besides is inverted by heating with 10 per cent of hydrochloric

inverted sugar, which turn the plane of polarisation acid, this inverted solution, if tested at the temperature to the left.

of o° C., will, after making the correction for the quantity Then we may suppose that C – i th - 8 =

= D.

of acid added, produce a deviation of 44 on the negative

side of the scale. In this equation the only known quantity is D, but what

If now we suppose that the law which Clerget found for we want to know is C. To find this quantity we make use of this fact, that if the solution under examination is temperatures between 10° and 35° holds good for all other heated with 10 per cent of hydrochloric acid, the whole left of the same solution of inverted sugar at any tempera

temperatures, we may easily obtain the deviation to the of the cane sugar will be converted into inverted sugar,

ture by subtracting from 44 one balf the number expressing while the other substances will not suffer any change this temperature in degrees Centigrade. Thus we shall From some experiments which I made with artificial mix. have for 10°, d= -(44-5)=-39; for 20', d--(44-10) tures analogous, as far as I could judge, to those which constitute the impurities of commercial sugars, I am led

=-34; for 28°, d= -(44 – 14) = -30, and for any tempe

rature, t, to believe that by heating with concentrated acid a certain change takes place in the deviating power of the impuri

dsties of commercial sugars. This change is, however, very

--(44- ),


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Divisibility of the Electric Light by Incandescence. {

May 16, 1879. If now we draw a series of parallel equidistant lines, clamour on telephones caused by the ordinary telegraph intersected by another series of lines, also parallel and currents on neighbouring wires. He had tried recently equidistant, perpendicular io the first, we may take on the the Bell telephone on a line from Dublin to Armagh, 95 horizontal base line or line of the abscisses, a space be- miles long, but the induction noises completely stifled the tween two lines corresponding to 1° C., and we may suppose speaking, whereas the Edison transmitter gave good that the space between two lines of the other series corre results. The clamour could be got rid of either by neu. sponds to a division of the negative side of the saccharo- tralising the induction currents or by eliminating the meter scale. If now, on every vertical line, starting from noises from the speech. He had taken the second line by the base line, we take a length proportional to the numbers experiment. Since the vocal currents differ from the ingiven by the equation

duction ones in potentia! and period, he attempted to make the latter discharge across the line to earth by fine needle points, and from a heated spiral of wire, in a vacuum,

leaving the vocal currents to pass on to the receiver, but and if we connect the extreme points of all these lengths without success. Also, since the vocal currents are alterby a line, we will find that it is a right line, because the nately positive and negative, whereas the induction ones equation

are of one sign, he tried to avail himself of the difference

in discharging power of positive and negative currents, but 44 -44 +

without success. He then tried to take advantage of the

difference of period or duration of the currents, the induc. is equivalent to the equation of the right line, y=a +b x, tion currents being longer. He therefore tried to break in which d=y, a= -44, b= , and x=t. If now we take again our equation,

the inductions by interposing a rapidly rotating current

interrupter, and to make the sections of the musical note d=-44+

obtained interfere with each other by means of an acoustic

interserence-tube, but practically failed in this also. He we will find that, if the law it expresses holds good to the mentioned these facts for the benefit of others who may end, the temperature at which the deviation becomes 0 is

be going over the same ground. 88° C.

Mr. WOLLASTON pointed out that a perfect cure for in(To be continued.)

duction on underground wires consisted in twisting the going and returning wire of the telephone circuit round each other.

Mr. Wilson then read a paper On the Divisibility of PROCEEDINGS OF SOCIETIES.

the Electric Light by Incandescence." By Joule's law the amount of heat developed in a circuit of resistance, R, by the

passage of a current, C=C:R; where Ris the resistance PHYSICAL SOCIETY.

of generators and connections, y, added to the resistance

of the light emitter or incandescent wire, P. Therefore, Ordinary Meeting, May 10, 1879.

since by Ohm's law,

Prof. W. G. Adams, President, in the Chair.

New member: Mr. J. Kestrell Evans.

we have Mr. WOLLASTON explained the construction of Gower's

E: improved form of Bell's speaking telephone. The older

Ciform, made of wood or ebonite, is open to the objections

(r+Pji' that it has a very weak voice, soon gets out of adjustment and from changes of temperature, and requires a twisted hand

EPP wire which is liable to break. Gower's form has a compara

C P=

ir + P* tively loud utterance, is constant, and does not require to be held in the hand, but may be laid on a table or hung on From this equation the value of P may also be determined. a wall, a speaking-tube leading from it 10 the operator's C2P is the amount of heat developed in the incandescent ear or mouth. The “call” for attra&ing attention is also wire. He infers that the smaller the mass of the within the Gower telephone itself; whereas, in the hand wire the higher the temperature generated in it, therefore telephone it is an auxiliary apparatus. Every organ of the mass of the wire should be diminished until the fusing, the old telephone has been modified to form the Gower point of the metal is almost attained. The question of The magnet in the Gower is of a horse-shoe form, very divisibility resolves itself into our being able to divide a powerful, the two poles being brought very close together, single incandescent source into a number of smaller ones and each pole is mounted with a small coil of fine wire giving the same total illumination. The author concludes The diaphragm is much thicker and larger than the Bell that this can be done by arranging the sub-divided sources diaphragm. The case is of brass, to expand equably, and in “multiple arc," or parallel circuits, provided the total a speaking-tube is fitted to the front of the diaphragm. mass, length, and sectional area of the united sources be The call consists of a musical reed attached to the dia. the same as in the original single source. The obje&ion phragm, so as to be opposite a small slit in the latter. that increased radiation from the various sources would To sound the call it is only necessary to send a sharp puff diminish the first total of light and heat can be met by of wind up the speaking.tube, and the reed gives out a making the smaller wires still smaller than is theoretically note which is heard throughout a room at the distant end. required so as to generate more heat. The author regards Speaking and cornet music was transmitted by the instru. the “voltaic arc" as probably falling under the same law, ment exhibited, between the third storey over the hall and the mass, however, being smaller in this case. the meeting. It was very distinct and audible several feet Dr. Coffin then exhibited a Trouvé Polyscope, which from the receiver. Speaking done some thirty feet from consists of a small hand incandescent platinum wire electhe transmitter was also sent. Conversation was likewise tric light, designed for illuminating the more inaccessible carried on while considerable noise was being made in the cavities of the body in surgical examinations. The current room.

is supplied by a Planté secondary battery, and the light is Prof. MCLEOD remarked that the timbre of this tele. talf enclosed in a small silver reflector, fitted with a conphone was very good.

venient handle. The apparatus is portable. Dr. Coffin Prof. W. F. BARRETT then gave an account of some found that it was open to several objections, which he has attempts which he had made to overcome the indu&ion' remedied. First, the heat generated made the lamp so hot



} May 16, 1879. The Vitriol Manufacture.

215 that it could not be held to the body for more than a very taken, a fatal case of poisoning is on record from an short time. He overcame this by making the reflector of over dose of tartaric acid, taken by mistake for Epsom double silver plates, and circulating water between by salts. Poisons are conveniently classed by the author means of india-rubber pipes from a bulb which can be under four heads—those which cause death almost imme. worked by the patient himself, thus serving to distract his diately, irritants, irritant-narcotics, and poisons affe&ing attention from the operation. Secondly, the secondary the nervous system. The fourth group is again subbattery exhausts itself in twenty minutes, and the light divided into narcotics, deliriants, convulsives, and those therefore goes out, while from twelve to twenty-four hours producing complex nervous phenomena. are required to re-charge it. Dr. Coffin has superseded it We cannot but consider it singular that though chrome by a Leclanché battery of 8 elements, made by Messrs. is mentioned among the irritant poisons no instructions Coxetter and Sons, in which the carbon pole is replaced are given for its detection. This is the more to be regretted, by a copper plate faced with platinum, and no porous as chromium compounds are used in the arts on a vast diaphragm is employed. This gives a constant light for scale, and are present in the waste-waters from dye and hours.

colour works, &c., whence they may find their way into streams, wells, &c. Potassium bichromate, even applied externally, often produces unpleasant symptoms--a fact

very familiar wherever “ chrome-blacks are much dyed. NOTICES OF BOOKS.

In the section on animal poisons we find a most interesting account of the secretion of the cobra, which the author has carefully examined. The active principle is not

germ A Manual of Practical Chemistry: the Analysis of Foods stable chemical compound, which Mr. Blyth has isolated

or organised ferment, but a well-defined and and the Detection of Poisons. By ALEXANDER

WYNTER and named provisionally cobric acid. BLYTH, M.R.C.S., F.C.S., &c. London: C. Griffin

The whole work is full of useful practical information, and Co.

and as far as we have been able to perceive it may be reThe first portion of the title of this book, when standing garded as trustworthy. An exceedingly valuable feature alone as it does on the back, scarcely leads the reader to —we believe original-is that the various pleas which may exped what is accurately enough described in the second probably be raised on behalf of a supposed adulterator or part. The work consists of two somewhat distinct sections, poisoner are here pointed out, and the expert is thus forethe one treating of the analysis of foods, with especial warned. We have also very full instructions as to the reference to their impurities—intentional or accidental- various channels through which different poisons may be whilst the other is devoted to the detection of poisons. introduced into the human system. Thus we have before us what might be pronounced two A defect which we hope see remedied in a future edi. distinct treatises, whose bond of union is mainly due to tion is the prevalence of typographical errors. The late the bookbinder.

Professor Gorup-Besanez is converted into Gorop Besaner; At the same time we feel perfeAly free to admit that Crantz, the historian of Greenland, becomes * Crzaut,” each of these parts has been compiled in a judicious and &c. In a tabular view of the composition of coffees from conscientious manner. In dealing with adulterations the different localities, taken from a German source, some author has selected the best and most recent methods; he words are left untranslated. Thus we read of Jamaica has appended certain useful legal decisions, and under and Ceylon “ Plantagen.” It should be “ Plantations." each chapter he has given the bibliography of the subject. We are pleased to see that Mr. Blyth does not under-rate the difficulties of food analysis and of toxicology; he ad. dresses himself to chemists, and does not, as some earlier

CORRESPONDENCE. writers have pretended to do, seek to make every man his own analyst. In speaking of the analysis of milk we find that he, like

THE VITRIOL MANUFACTURE, most practical authorities, is able to confirm the substantial invariability of the “ solids not fat " as existing in un.

To the Editor of the Chemical News. sophisticated samples. He admits that the publication of SIR,--Dr. Lunge seems to have misunderstood the purport a normal standard allows a certain amount of watering to of my letter. I did not intend to prove that an apprebe practised, but he fears that the bulk of commercial milk ciable loss was actually experienced in the Glover tower ; in this country is below the lowest estimate of the Society I wrote to point out that all fear of appreciable loss of of Public Analysts. We must, moreover, warn him that nitre in the Glover tower had not yet vanished. I it is not in all cases safe to discuss and criticise, even published some figures simply to show the possibility of approvingly, published analytical processes, We have such a loss being quite appreciable. heard of one case where such criticism, which necessarily It would not from my point of view be necessary to involves quotation, was met with the threat of an action reply to Dr. Lunge at all, since his remarks How from for infringement of copyright. The remarks on unhealthy this misunderstanding, but as some of these remarks are and abnormal milks are very interesting. The author con- directed against my ability of weighing arguments, I feel siders it demonstrated that a disease similar to, if not it a duty to myself to make the following statements. identical with, tuberculosis may be propagated from animal Until very recently the loss of nitre was by no means to animal by means of the milk derived from a diseased generally understood to be to so large an extent due to cow. He considers that phthisis is very rare among the reduction of nitrogen compounds. For example, cattle, and that when so affected their milk rapidly de- Lock's Treatise on the Manufacture of Sulphuric Acid, creases in quantity. The chemical qualities of the milk dated 1879. decidedly inclines to the belief that Mr. Davis's secreted during cattle plague, pleuro-pneumonia, and views on the subject are the best explanations yet given anthracoid affections have not been duly ascertained. of the loss of nitre. Dr. Lunge's treatise, just published

The adulteration of tea Mr. Blyth thinks is substantially in German, lays more stress on the loss of nitre incurred effected abroad, and is decreasing.

by reduction to nitrous oxide in the chambers. But the Turning to the toxicological section, we find a remark whole tenor of the explanations given of the reactions quoted from Dr. F. Mohr, which though mainly judicious causing such loss is such as to produce the impression is on one point open to question. This distinguished che- that these reactions occur only in isolated places in the mist says—" What relation sal-ammoniac, saltpetre, alum, chambers, viz., near the steam-jets, and is not at all caltartaric, citric, and acetic acids, &c., have to toxicology culated to give an idea of the magnitude of this loss, we cannot conceive.” Yet, unless we are greatly mis- which Dr. Lunge now puts down at 75 per cent of the

I can

The Vitriol Manufacturé.


May 16, 1879. nitre used. An attempt to give a measure of the loss even trator, but that does not imply that the Glover tower is if only approximately, I have not found in this exhaustive perfect, nor exclude the possibility of improvement. and very able treatise. I consider it therefore a gain to In estimating the share of loss of the chambers I made have elicited from so high an authority as Dr. Lunge the use of Mr. Davis's figures. Mr. Davis defended these admission (even if conditionally only) that the amount of very figures as those he was most sure of. I have, hownitre lost in a manner not yet clearly understood is 75 per ever, some results of daily testings extending over three cent, or more, of that used.

months of the exit gas of a set of chambers having neither This “big margin ” of course is affected by all the Glover nor Gay-Lussac tower attached, and these results errors in estimating the losses from other sources, but it show that the amount of nitrogen escaping in form of its is quite certain that the statements I furnished err on the acids is within a small amount (20 per cent) equivalent right side. Dr. Lunge differs from me only in the distri- to the nitre potted. All the conditions which are necessary bution of this “big margin.” Whereas I think a portion to cause a reduction of the nitrogen compounds to a lower of nitre (and I have many reasons for thinking so) is de degree of oxidation than nitric oxide I conceive to be composed in the Glower tower, Dr. Lunge considers the present in the Glover tower to an equal, if not a greater, whole of it destroyed in the chambers. He would have degree than in the chambers. The sulphurous anhydride been more consistent if he had used a similar phrase to here in its greatest concentration is associated with all one occurring in his treatise, to the effect that certainly the steam evolved in the Glover tower, to react upon the Glover tower is in this respect no worse than any other nitric oxide in the nascent state at a temperature much denitrator.

higher on the average than that of the chambers. To some extent, however, Dr. Lunge seems still to

see no valid reason in what Dr. Lunge has think that part of the “big margin" must be accounted brought forward to arrive at the conclusion that the loss for by the oxidation of arsenious acid to arsenic acid in in the Glover tower has " vanished into thin air,” or, as the Gay-Lussac tower, when, he remarks, that my views he formerly expressed himself, is as small as a " differential conflict with “very careful investigations of M. Hjeldt.” quotient," whatever that expression is meant to convey. But permit me to point out that these “ very careful in. Still less can I see any great wisdom in so easily acquitting vestigations” are of the same type as Mr. Davis's. Both the Glover tower of all share in the destruction which is authors discovered arsenic acid in Gay-Lussac vitriol, evidently going on in the system, and for which, I am both came to the conclusion that it was due to oxidation fully convinced, the chambers are not wholly responsible. by nitrous anhydride at the expense of an equivalent of - I am, &c., nitric oxide. Neither of the two gives experimental

FERDINAND HURTER. proof of this assertion; while Mr. Davis tries to find the Laboratory, Gaskell, Deacon, and Co. resulting nitric oxide in the exit gas of a number of works,

Widnes, May, 1879. M. Hjeldt is satisfied with simply calculating the probable loss of nitre due to this supposed reaction. I have at.

THE VITRIOL MANUFACTURE. tempted in more ways than one to oxidise arsenious acid by means of nitrous acid in presence of strong sulphuric

To the Editor of the Chemical News. acid. I have allowed the reagents to act for seventy-two Sir, I do not wish to take up more of your space than I hours at ordinary temperature, and for several hours at am obliged, but it seems to me necessary to state that in temperatures up to 230° F., without being able to obtain testing vitriol exits by a continuous system a Bunsen pump a single bubble of any gas, either nitrogen, nitrous oxide, and meter is not necessary. An 8-litre bottle properly or nitric oxide. I have after repeated experiments come arranged is more than sufficient for eighteen hours' work, to the conclusion that arsenious acid cannot be oxidised and if that quantity of gas be drawn out in such a manner to arsenic acid in presence of strong sulphuric acid so as to accurately sample the whole number of cubic feet of easily as to constitute a source of loss in the manufac- gases passing, one cubic foot, or even less, will serve every ture of sulphuric acid. Thus I am convinced that the purpose. One cubic foot of the exit gases in many of my “big margin” must be accounted for otherwise. Where the experiments has been a sample of at least 1,200,000 cubic whole of the site is introduced into the Glover tower feet passing away. But what I principally want to point there remain only this apparatus and the chambers for out (and which I did point out in my last, only it seems to the distribution of the loss.

have vanished in transit) is that both Hurter's and Lunge's Dr. Lunge thinks my fallacy consists in not having theory of the chemical loss of nitre in the chambers will brought forward one particle of proof that any part of this not work. Hurter ascribes 20 per cent loss, due to the " big margin ” must be accredited 10 the Glover tower, adion in the chambers. Lunge says 75 per cent. Now and he produced, what is no doubt meant to be an excel. let us examine both of these. lent proof, that the whole of it must be ascribed to the A works with five large chambers was making 100 tons chambers.

of vitriol per week, and they were using to produce this Dr. Lunge cites the results of two French works. In 3 tons of 'nitrate of soda per week; they used no towers, one of these (Scheurer-Kestner), where no Glover tower made always a good production from the ore burnt, and the is used, 4-7 of nitre per 100 of sulphur were consumed, escaping oxygen was 6-2 per cent by volume of the exit and Dr. Lunge calculates that 75 per cent were decom- gases. The total acidity of the exit gases was always posed inside the chambers. If that is really so, how low-about 2'3 grains of Na2CO3 neutralised by one cubic could the other works (Maletra, of Rouen) where nearly foot. After working in this way for some years this firm the same amount of nitre was used per 100 of sulphur, decided to erect one denitrating column and two absorbing save 35 per cent of the nitre, simply by introducing a columns : directly they started to work there took place a Glover tower. There would on Scheurer-Kestner's basis great reduction in the quantity of nitre used, and the nor be at the outside 15 per cent to be saved, and based on mal quantity soon became 16 cwts. per week. Dr. Lunge's calculation I should say that the introduction Now let us examine these results closely, and the amount of a Glover tower in Scheurer-Kestner's works would, as of nitre destroyed by the chambers must be reckoned on far as denitration is concerned, be practically useless. the original quantity used belore the towers were ereâed, Dr. Lunge evidently has forgotten to charge Scheurer- as your correspondents have not inferred that the introduc. Kestner's denitrator with part of the loss incurred. For tion of towers will cause the destruction of nitre in the a saving of 35 per cent in such works is only possible if chambers to be any less, and we have no published experithe mode of denitration formerly in use is more disastrous mients which even hint that this might be the case. These than that by the Glover tower.

chambers, then, actually used 60 cwts. of nitrate of soda I have no experience of any other method of denitra. per week. tion except that by the Glover tower, and for ought I can Hurter states twenty per cent is destroyed in the chamsay to the contrary it may be the very best form of deni- l bers; this is equal to 12 cwts.

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