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Study of Chlorine Substitution.
or a butyl-methane, H3C.C4H9, or propyl-ethane, H5C2.C3Hy, or diethyl-methane
He notates the chloride as
July 14, 1876.
and as far as the nature of the paraffin is concerned one is as correct as the other; but they are all condensed expressions of the one true formula
We stay not to discuss such elements of difficulty and hypothesis, but we do ask, What is the outcome thereof in the region of practical manipulation?
The most simple and fertile distinctions, appreciable even to the amateur mind, are wholly ignored, while learned Professors are discussing methylen dispositions and polyatomic peculiarities worthy of medieval metaphysics.
That Prof. Odling is amiably and earnestly desirous to extend our knowledge of isomerism no one will doubt; but, standing before his methylen basis of terminology and classification, there are simpler matters, more within reach, which demand a juster and clearer appreciation.
When chloro or nitro substitutions subsist isomerically, the A B C of the matter is to determine where the chlorine or other radical has alighted, "whether in a methyl or in a methylen residue," &c.
Per contra, we hold that in such cases, whenever two or three isomers subsist, as a general rule, the isomeric differences are due to the radical itself, and equally subsist when the Cl or (NO) is withdrawn ; and that the A B C of the matter is to distinguish between a chloride and a chloro-radical; and, further, that this distinction is a real one in fact, as well as a primary one in chemical ethics, extending also to the H of the hydride.
Some chemists take great pains to insist that in methane no difference is appreciable among the H elements; but, taking methane and mellissane as extremes, may we not fairly ask for some appreciation of the volumetric and other differences due to the H elements?
This may not be capable as yet of absolute demonstration, and there may be difficulty in isolating the radicals without dedoublement or condensation ; but the hypothesis is deserving of respect and further research, that the 61 H elements of melissyl are condensed into one volume; and that the added one H of the hydride or chloride doubles the entire volume.
If chemists can distinguish between the atomic volumes (solid) of O=12:2 in acetyl, and O=7.8 in alcohol, surely they may be able to appreciate the difference between H in methyl or mellissyl and the H of their hydrides, seeing that one is, perhaps, one hundred fold more condensed than the other.
And similarly with the chlorine of chloracetyl, as compared with that of acetyl chloride.
Whether we have ammonia, trimethyl ammonia, or tristearyl ammonia, who is there that doubts that these condensations do really represent so many H equivalents, both chemically and volumetrically; and whether this hypothesis in all its bearings will pierce the clouds of prejudice, and ripen into true theory is not at all the present question, which is rather as to what advantages have accrued from a studied disregard of the plainest facts, and in illustration thereof we confine a few remarks to chloracetic acid.
At the outset, we may assume for the elements so-called at least two isomeric forms:The true chloracetic acid, (C4H2CIO2)O.HO=C4H3O4Cl, glycolyl chloride,(CH3O4) C1=C1H2OČI."
Dr. P. Romer digested a mixture of mono-chloracetic acid with strychnine at 180° C. for several hours, and obtained a new base: that he combined with platinic chloride, giving the salt C23H2404NHCI.PtC12.
Glycolic acid or
CH3 02C38H21O8N, acetyl morphia
+morphia - 2HO=
C4H806C38H21O10N, glycolyl morphia]
In the reactions with true chloracetic acid there is a
We have enlarged elsewhere on the same want of discrimination in respect of Armstrong's invaluable epitome of the science (see CHEMICAL NEWS, vol. xxxii., p. 2), and could give many other illustrations, but in utmost brevity we conclude with a recent discovery of "melid acetic acid." The others are curious, but this one is much more so, and the determination to make it an "acetic acid," involves an inverse audacity, which is as marvellous as it is racy. The idea is that one H of acetic acid is replaced by the radical or base "melamid;" but what is melamid ? Thanks to Hofmann we know pretty clearly what melamine is, both as a free base and as evinced in saltic types. Now this feature may be very nice for a "residue," but it is very damnatory for a radical or base, having a mono equivalence; and it irresistibly tempts us to turn the whole thing upside down, when, lo! the result is no acid at all, but a "glycolyl-melamine," behaving chemically and typically as a substituted melamine, and acetic acid probably has no existence, either before or after the reaction.
Melamid, then, is said to be "melamine - H1."
The sulphate or nitrate of a melid acid looks very much like a melee of confusion, whereas melamine gives mono salts exactly like those above.
Truly chemists stick at nothing in order to carry out their preconceptions, and in sight of such results one is tempted to ask Cui bono?
It may be urged that, admitting an acetyl body most normally gives an acetyl substitution, yet that exceptional cases of oxidation may transform that radical into glycocol (or oxacetyl). And some may further contend that the above bizarre types are models of atomic penetration and artistic ingenuity derived from a study of the formative and transformative reactions involved.
They are nothing of the kind; they are fanciful pleasantries, the legitimate offspring of fanciful hypothesis; and against this torrent of passing fashion I can do nothing but protest, and, with one leg in the grave, I can hopefully retire with the certain conviction that truth will be paramount, and that a better time is coming, when science will be more popularised, and simplicity of conception will no longer be tabooed as necessarily superficial knowledge.
DEVELOPMENT OF THE CHEMICAL ARTS DURING THE LAST TEN YEARS.*
By Dr. A. W. HOFMANN.
(Continued from p. 5.)
Chlorine, Bromine, Iodine, and Fluorine.
FOR many purposes, especially in the manufacture of sugar, there is required a hydrochloric acid free from sulphuric acid, iron, and arsenic. Very various proposals have therefore been made for obtaining a pure acid from the arseniferous product. Thus, Houzeau,† in order to obtain the acid free from arsenic distils the crude acid, adding 03 grm. pulverised chromate of potash to 3 litres, and, in order to protect the arsenic acid produced by the liberated chlorine from the reducing action of the hydrochloric acid, he causes during the distillation a continued stream of a solution of chromate of potash of tenfold the strength to be added. The escaping hydrochloric acid gas is freed from the accompanying chlorine by means of copper turnings and is then conducted into water. This process, however, is scarcely applicable on the large scale, as chlorine is necessarily evolved in very considerable what costly. P. W. Hofmann, of Dieuze, on the other quantities, and its absorption by means of copper is somehand, has successfully introduced the following method for purifying hydrochloric acid:-A vessel with a doubly perforated earthenware stopper is filled with hydrochoric acid to the extent of one-third, and sulphuric acid of SP. gr. 1848 is introduced by means of a funnel capable of being closed. The hydrochloric acid gas, which is given off very regularly, is washed in a Woolff's bottle and absorbed by distilled water in a receiver.
The evolution of gas ceases as soon as the sulphuric acid has fallen to the sp. gr. 1'566, in which case it only retains 032 per cent of hydrochloric acid. The sulphuric acid thus diluted is either employed direct in the manufacture of sulphate of soda, or it is re-concentrated, the expense of which amounts to 1 franc per 100 kilos. As 100 kilos. of sulphuric acid thus yield 40 kilos. hydrochloric acid of sp. gr. 1'181, 100 kilos. of pure hydrochloric acid prepared by this process are 2 francs dearer than the crude acid. Fresenius,|| however, remarks that the acid thus purified is not quite free from arsenic, the gas evolved containing arsenic at every stage.
Bettendorfs prepares pure hydrochloric acid by utilising the fact that arsenious acid in a concentrated hydrochloric solution is thrown down by protochloride of tin as a brown precipitate composed of arsenic with 15 to 4 per cent of tin. He mixes the concentrated acid with a concentrated solution of stannous chloride, filters off the precipitate, and distils, thus obtaining an acid perfectly free from arsenic.
This is confirmed by Mayrhofer, but Hager** adds that if all the arsenic is not removed by filtration the distillate again becomes arseniferous. Dietz treats the hydrochloric acid with sulphuretted hydrogen, whilst
*"Berichte über die Entwickelung der Chemischen Industrie Während des Letzten Jahrzenends."
+ Houzeau, Compt. Rend., lix., 1025. Wagner, Jahresber., 1865, 251. P. W. Hofmann, Ber. Chem. Ges., 1869, 272. Journ. Analyt. Chemie, 1870, 64.
§ Bettendorf, Dingl. Pol, Journ., cxciv., 253. Wagner, Jahresber., 1869, 219.
Mayrhofer, Ann. Chem. Pharmacie, clviii., 326. **Hager, Wagner Jahresber., 1872, 262.
Reducing Action of Phosphine.
Engel employs hyposulphite of potassium for the same purpose. Of all these processes that of P. W. Hofmann is probably the only one used on a large scale. The pure hydrochloric acid required in the sugar manufacture is chiefly prepared in certain small establishments which make their sulphuric acid from sulphur, or which have at command non-arseniferous pyrites, e.g., at Saarau, in Silesia.
(To be continued.)
REDUCING ACTION OF PHOSPHINE.
PHOSPHINE (PH) exerts a powerful reducing action upon sulphuric acid (SO2HO2). When passed into the strong acid the gas is absorbed rapidly at first, without any visible change, but when the acid has become saturated, and the action of the gas is still continued, the acid rapidly becomes heated sufficiently to ignite the phosphine. If the sulphuret be kept cool by a stream of water and the gas passed into it in excess, reduction to sulphurous anhydride, SO2, with separation of sulphur takes place.
The action may be thus represented
3(H2SO4)+2PH3=2SO2+S+2(H3PO4)+3H2. Hydric sulphide may be produced, but, if so, is decomposed immediately by the SO2.
If the action be continued sufficiently long, the acid being kept cool, it becomes so thick and viscid with the separated sulphur that the vessel may be inverted without its contents escaping.
I did not propose that my experiments should have any special accuracy, such as would be required in critical examination of the relative merits of two similar beams, but only that they should be trustworthy, as shewing that flexibility has an influence-an influence greatly to the disadvantage of badly-designed beams, and not entirely to be overlooked in those of ordinary construction, but which almost vanishes in the beam in which Mr. Bunge has combined the advantages of superior mechanical principles with unusually good material and excellent workmanship.
I commenced with a beam of no value-a common
dispenser's box-end beam, made of brass, its length between terminal bearings being 6-7 inches and its weight 680 grs. I bound it down against the edge of a strong steel bar—a file, in fact-the box-ends forming the terminal supports of the beam, while the pressure was applied to the centre, and the bending estimated by the diminution of the distance between the centre of the beam and the bar. This movement was necessarily very small, and the value of the observations must depend upon the extent of this small movement being fairly estimated. After a few preliminary attempts the method I adopted was to cement a slip of glass upon the bar projecting beyond its edge
* Read before the Newcastle-upon-Tyne Chemical Society.
towards the beam, and a piece of mica upon the beam projecting over the edge of the glass; the movement of the edge of the mica over the edge of the glass was observed by a microscope magnifying several hundred diameters, and measured on an ordinary scale of inches and fractions laid upon the microscope stage, and observed with the left eye, while the mica was observed with the right eye through the microscope.
The pressure representing the load was applied by means of a spring, as the observations were most conveniently made with the movements in the horizontal plane. The spring used was a pair of microscope pliers having a distance of half an inch between their points, and it was found by experiment that each one-sixteenth of an inch compression represented a pressure equal to nearly 500 grs.-sufficiently near for my purposes. This spring was held in place by pins in the board which carried the whole arrangement. I placed one end of the spring just in contact with the middle of the beam, while the other was free to receive pressure, the pressure being regulated by fixing a pin in the line of motion of the free end and at such a distance as limited the compression of the spring to the degree which was required to produce the pressure desired. When the pressure was 500 grs., that is, equal to 250 grs. in each pan, the flexure equalled of an inch, and with four times the pressure the movement was inch, thus confirming the first observation. The observations were repeated many times, with only such differences in the measurements as would naturally result from the nature of the experiment.
The second beam operated upon was a German dispensing beam of better quality than the above. Being of a different shape, it was found more convenient to fix one end and the middle, and apply the pressure to the free end of the beam, using the spring in the same manner as before, but adopting a new arrangement for microscopic observation. A microscope slide cemented to the end of the bar had diamond scratches upon its upper surface; a similar slip laid upon it with diamond scratches upon its under surface; the end of the beam rested upon this upper slip of glass, and was made to adhere to it with cement. The diamond lines being on contiguous surfaces of glass were readily brought into a sufficiently good focus for work, but a lower power was necessary in consequence of the thickmade. A magnifying power of 125 linear was, however, ness of the glass through which the observation had to be readily applied and found quite sufficient for the purpose. A drop of oil interposed between the glass slips rendered the focusing more satisfactory, but the motion rather less free. When the pressure equalled 500 grs. in each pan, the pressure equalled 2000 grs. in each pan, the bending the bending thus observed equalled 1-1000th inch, and when was, inch. These flexures must be halved to compare
them with those of the first beam.
tended to carry 1000 grs. on each pan, and turn with The third beam examined was one of Oertling's, inof a gr. The examination was conducted in the same manner as the last. The bending with the equivalent of 1000 grs. in each pan was zo inch, which observation, after being several times repeated, was further confirmed by doubling the pressure and finding that the flexure was also doubled.
manner; being designed to carry 3000 grs. in each pan, Finally, Bunge's beam was examined in the same and turn with gr. it was not to be expected that flexure should be observed to a measurable extent with light pressures. I found them too small to be satisfactorily estimated with pressures less than 2000 grs. in each pan; under this load the bending was inch. venient form for comparison. The beams are arranged in The following table shows the above results in a conthe order in which they were examined. Their order also coincides with the development of the mechanical principles upon which they have been designed, and indicates progressive improvement in their working qualities, the second being both longer and lighter, yet less flexible than
July 14, 1876. Effect of Flexibility on the Working of Chemical Balances.
the first, as a consequence of the better distribution of its mass; so in comparing Bunge's beam with Oertling's we have both the weight and flexibility reduced to less than one-third, and the figures might have been still more in favour of Bunge's had it been practicable to make an equal reduction in weight upon those parts of the beam upon which there is little mechanical strain, but as in these parts there is not much excess in the old beams, there is not the same scope for reduction.
Fall in Centre of
Gravity of Load.
In endeavouring to calculate the influence which the bending (as estimated by the preceding experiments) has upon the sensitiveness of the beam, I have not attempted to follow the Algebraic method as expounded by Prof. Aldis, but have contented myself with the methods of plane geometry and arithmetic with which I am more familiar, but which appear to me to tend to precisely the same conclusions.
If we take c as the centre of a circle, A B and E D its diameters, E D also representing a beam of which C B is the pointer, two or three simple propositions will enable us to calculate the sensitiveness of the beam and the effect that bending has upon it. Let the lines A H, H B, and H 1, be drawn, the latter being perpendicular to C B. IB will have the same ratio to H B that H 1 has to a H. Wherever the point I may be placed, these ratios remain
the same. Now, let CH be the pointer deflected by a weight added to the beam at D, and having swayed the beam to the position FG, the weight and the distance taken together represents a certain mechanical power. If it be a foot-pound, and the beam has come to rest at F, then the work performed by this power must be a footpound also. Foot-pounds being too large for present use, inch grains or inch m.grms., will be more convenient.
If, now, be suppose C to be the fulcrum, and the centre of gravity of the beam, gr. added to D and x gr. added to B, the length of the beam being 10 inches, the fall of D being inch, the deflection at B will also be inch-the fall of 1 gr. inch rob of an inch gr. The deflection at B being inch, is, of the length AB, and for practical purposes at these small deflections also 1 of the length of A H. Now, as IB bears the same ratio to this as this inch bears to AB (10 inches), the weight added to B has been raised vertically of 1% of an inch, or 10%, and as this work done equals
τούτο of an ineh gr., of a gr. must be the weight so raised. Now, suppose the beam to weigh 1000 grs., and that no weight had been added to B, while the same deflection of the pointer had taken place and the same work consequently had been performed, the centre of gravity of the beam must have been raised by the turning just so much as to equal boo of an inch gr., and that this may take place the centre of gravity must be as many times nearer the fulcrum as the weight of the beam is greater than that previously supposed to be acting at B. As its weight is 10,000 times greater, its distance will be Toboo of CB (5 inches), or o'002 inch. If it be admitted that the distance between the centre of gravity of the beam and the fulcrum must be so small under these circumstances, and smaller still when the beam is heavier of the same length, the amount of bending which I have obtained is sufficient to interfere with its sensibility; and the difference in flexibility between Bunge's beam and the forms at present in use in the laboratories, is sufficient to give Bunge's a distinct superiority in this respect.
In estimating the effect of the bending of the beam, it must be remembered that the centre of gravity of the beam does not fall to the same extent as the bending takes place, but only to a smaller extent, and an extent which it is not practicable to estimate; but the virtual centre of gravity of the load falls to the full extent of the bending.
In the above illustration, that of a beam weighing 1000 grs. with its centre of gravity o'0005 below its fulcrum, and its end bearings on a line with its fulcrum when not strained, if we suppose a bending to take place when loaded such as takes place in the Oertling beam examined, then the resistance is increased from 1000 X 0'0005 to this product, + 2000 × 0.0004-that is, the weight of the pans with their load multiplied by the fall which has taken place in their centre of gravity, leaving out of the question the falling in the centre of gravity of the beam due to its bending. Thus the resistance due to bending would bear to the original resistance the ratio of 8 to 5.
Supposing the pointer of the Oertling beam to move o' inch with gr., I calculate the centre of gravity to be 0'00027 below the fulcrum, and its resistance to the supposed movement would be thus multiplied by its weight 1786 grs. and the additional resistance due to bending would be 2000 x 0.00041. By this calculation the resistance due to bending is to the original resistance as 82 to 48.
Supposing the pointer of Bunge's beam to move I m.m. with o'r m.grm., I calculate the centre of gravity to be 0.00304 inch below the fulcrum, and its resistance con sequently 600 × 0.00304; while 1000 grs. in each pan = 2000 X 0'00012 (the extent of its bending), gives the additional resistance consequent upon its bending under its load. The resistance due to bending is to the original resistance as 24 to 182.*
Since the distance between the fulcrum and the centre of gravity may be indefinitely decreased, the sensitive. ness of the beam may be indefinitely increased provided the mechanical defects of the beam do not stand in the way, but length and its consequence-either considerable weight or palpable flexibility-are prominent obstacles to this mode of increase of sensibility, and the palpable thickness of the knife edges is another obstacle. In the ordinary steel knife edges, however fine they may be at
* In a balance recently designed by Prof. Mendeleef, the length of the beam is rather less than Bunge's, and it is stated to turn with 1-1000th gr. when loaded with 15,000 grs. I have not seen this balance, nor even a detailed description of it; such particulars as 1 have are quoted from the Pharmaceutical Journal of March 11, 1876. Mendeleef accomplishes this extreme sensibility by adding micrometer scales and cross threads at the ends of the beam, and a telescope for their observation-a refinement which was introduced by Prof. W. H. Miller, and which, while it greatly increases the delicacy of the observation, removes it beyond the sphere of convenient daily appliances. I had not seen any notice of Mendeleef's balance til after I had drafted my present communication.
New Method for the Detection of Copper, &c.
first, they can scarcely be brought with pressure upon the agate planes without a palpable thickness being imparted to them.* Those I have examined had a thick ness visible to the naked eye, while Bunge's, made of quartz crystal, I have not succeeded in seeing with the aid of a lens. I must admit that a fine edge would be much less readily seen in a material like crystal than in metal, but it must also be admitted that the greater hardness of the stone would give a permanence to the edge which a steel edge would not possess. Suppose we admit that in the crystal edges and planes the imperfections of a fulcrum are as nearly as possible eliminated-that the flexibility has been reduced to its smallest practical amount by the use of the girder form adopted by Bunge -that the sensitiveness is under our command by screwing up the centre of gravity, and that the quickness has been obtained by reducing the length of the beam, where lies the practical limit to the smallness of the weight which will turn the beam? Mathematics would teach us that any weight, however small, would turn the beam to some extent, and that the limit is the limit of our vision. This points to the last particular in which Mr. Bunge has improved upon the old models. Having secured movement by the means already pointed out, he has magnified the motion by increasing the length of his pointer, and this is of more importance than would at first sight appear, for it gives the principal advantages of a long beam without its failings, for the long pointer adds very little to the slowness of turning, and nothing to the flexibility.
In making these remarks I would not have it supposed that I am writing up the performances of Bunge's balance. I have simply endeavoured to understand and to explain oy what principles the maker has obtained the very excellent results which we all admit.
I must also add, that while I have connected Oertling's name with a balance not equal to Bunge's, I do not imply that Oertling's workmanship is inferior; on the contrary, requiring for the sake of comparison to experiment upon a beam of the form in general use, I preferred to take one of Oertling's on the ground that his name was a guarantee of good quality.
A NEW METHOD FOR THE DETECTION OF
By MALVERN W. ILES, Ph.'B.,
In working upon the cyanogen compounds, the experimenter knows not what singular and unexpected results he may bring about at every step. That his results are often very highly characteristic is well proven by the beautiful shades of blue, green, red, white, yellow, and brown produced from this radical. Some of these tints are, however, very far from being beautiful; thus we have a dirty, dark yellowish brown. Other shades may be described as brownish yellow, reddish brown, brownish grey, deep reddish brown, yellowish brown, orange-yellow, and various shades of white.
July 14, 1876.
Hydrocyanic acid can scarcely be preserved alone, even when enclosed in a carefully stopped bottle; it soon darkens, depositing a black substance containing carbon, nitrogen, and perhaps hydrogen: ammonia is formed at the same time, and many other products. Light favours this decomposition. Dilute solutions soon become turbid, but not always with the same degree of rapidity, some samples resisting change for a great length of time, and then suddenly solidifying to a brown pasty mass.
When hydrocyanic acid is mixed with concentrated mineral acids, as hydrochloric, the whole solidifies to a crystalline paste of ammonium chloride and hydrated formic acid.
On the other hand, when dry ammonium formate is heated to 392° F., it is almost entirely converted into hydrocyanic acid and water.
The experimenter may also produce, at any step, cyanides, cyanates; cyanic and cyanuric acids; hydrated cyanic acid, hydro-ferro and hydro-ferricyanic acids, or the combination of the same with bases. I might further cite as an illustration of these remarkable changes, that cyanic acid when mixed with water is decomposed almost immediately into acid carbonate of ammonium; that pure cyanic acid on standing soon changes spontaneously, with a sudden elevation of temperature, into a solid, white, opaque, amorphous substance, called cyamelide. Furthermore, this curious body has the same composition as cyanic acid, but is insoluble in water, alcohol, ether, and dilute acids; it is soluble in strong oil of vitriol by aid of heat, with the evolution of carbonic acid and the production of ammonia. When boiled with a solution of caustic alkali it dissolves with the disengagement of ammonia, and a mixture of cyanate and cyanurate of the base generated. By dry distillation cyamelide is again converted into cyanic acid.
The artificial production of urea, a product of the human body, from ammonium cyanate, marked a new era in organic chemistry, and constitutes one of Wöhler's greatest discoveries.
Urea is decomposed, by the aid of heat, into cyanuric acid and ammonia. Cyanuric acid is changed by a very high temperature into cyanic acid. The study of cyanic and cyanuric ethers, which were discovered by Wurtz, has led to very important and curious results.
In this connection may be mentioned that curious body, fulminic acid, which is isomeric with cyanic and cyanuric acids; also fulminuric acid, isomeric with cyanic, fulminic, and cyanuric acids. In short, cyanogen and its compounds are to me a perfect marvel! It is, I think, one of the main keys to the intricate secrets of Nature, and when its behaviour is properly understood will unlock the door to various phenomena in organic chemistry now inexplicable.
While working upon the ferro- and ferri-cyanides of nickel and cobalt, with reference to a qualitative detection of nickel in the presence of cobalt, I was led to study the reactions of various other metals with the reagents above mentioned. Some of these reactions were so striking that a qualitative separation immediately sug gested itself. For example. a solution of potassium ferricyanide (1 part salt to 38 parts water) yields with copper a dirty yellowish brown precipitate, with bismuth a yellowish brown, and with cadmium a light yellow precipitate. The copper and cadmium ferricyanides were found to dissolve entirely in potassium cyanide in slight excess, while the bismuth separated in white floccules. Using this fact as a basis, my mode of procedure may be briefly stated as follows:-Proceed with the H2S group up to the point where Cu, Cd, and Bi are obtained in solution toinso-gether, as usual, care being taken not to have too large an excess of free acid; then proceed with the following scheme :
The deportment of various reagents with the cyanogen compounds may give rise to products entirely nullifying the experimenter's theoretical considerations, but frequently very highly characteristic of the element with which he is experimenting.
As an illustration of the singular changes which cyanogen compounds undergo, I may cite the following :An aqueous solution of cyanogen rapidly decomposes, yielding ammonium oxalate, paracyanogen, a brown luble matter, ard other products.
* Mendeleef says in the ordinary arrangement of steel knife edges upon agate bearings the wearing not only damages the stability of the balance but also quickly destroys its sensibility.
A Paper read before the Chemical Section of the New York Academy of Sciences.-American Chemist,