Obrazy na stronie


= 22'00 =I0'00



} February 21, 1879. Absorption of Gases by Charcoal.

77 divided by two or it is the atomic weight and


specific gravity multiplied into each other, 16 x 16, and VOL. XXXIX. No, 1004,

divided by two


= 128. Nitrogen was expected to act in a similar way, but it refused. The average number of the latest inquiry is

4:52, but the difficulty of removing all the nitrogen from ABSORPTION OF GASES BY CHARCOAL.

charcoal is great, and I suppose the correct number PART II.

to be 4:66. Taking this one as the weight absorbed, ON A NEW SERIES OF EQUIVALENTS OR Molecules. 14* 4:6665'3, or it is I4. Oxygen is a dyad; nitrogen By R. ANGUS SMITH, Ph.D., F.R.S.

3 a triad.

We have then carbonic acid not divided, but simply In the Transactions of the British Association, 1878, 22 squared=484. Norwich, on page 64 of the Abstracts, there is a prelimin- Time is required for full speculation, but the chemist ary notice of an investigation into the amount of certain must be surprised at the following:gases absorbed by charcoal. I made the inquiry from a

6 belief previously expressed in a paper of which an abstract Carbonic oxide

volumes. is in the Proceedings of the Royal Society, page 425, for Carbonic acid, CO2

6+16 1863. I said in that paper that the action of the gas and Marsh-gas, CH4..

6+4 charcoal was on the border line between physics and chem- Protoxide of nitrogen, NO 8+4.66 (N) (4:9) = 12:06 istry, and that chemical phenomena were an extension of the physical ; also that the gases were absorbed by char- roborated lately, but so remarkably carrying out the prin

These four results belong to the early group not cor* coal in whole volumes, the exceptions in the numbers cipie of volume in this union, giving numbers the same as being supposed to be mistakes. The results given were :

those of weight in chemical union, that they scarcely Hydrogen

require to be delayed. Oxygen ..


I am not willing to theorise much on the results; it is Carbonic oxide


here sufficient to make a good beginning. We appear to Carbonic acid


have the formation of a new series of molecules made by Marsh-gas

squaring our present chemical atoms, and by certain other Nitrous oxide


divisions peculiar to the gases themselves. Or it may be Sulphurous acid


that the larger molecule exists in the free gas, and Nitrogen


chemical combination breaks it up. These new and

larger molecules may lead us to the understanding of It was remarked that the number for nitrogen was chemical combinations in organic chemistry and whenprobably too low; I had some belief that the charcoal ever there is union not very firm, and may also modify retained a certain amount which I had not been able to

some of our opinions on atomic weights and the motion estimate. For common air, the number 40065 crept into the

Of course, I cannot pretend to give the result of these paper or abstract instead of the quotient 7:06

results; but as we have here the building up of a molecule i considered the numbers very remarkable, but was afraid by volumes, so as to form an equivalent of physical comthat they would be of little interest unless they could be bination analogous to the chemical equivalent, it is impos. brought more easily under the eyes of others; my experi- sible to avoid seeing that it indicates the possibility of ments were somewhat laborious; the exact numbers were

our present equivalents being made up in a similar seldom approached by the single analysis, but were wholly the result of a series of irregular averages and I did not expect these numbers; but I certainly, as my apparently irregular experiments. The cause of this was previous paper showed, had in full view a necessity for clear, as I believed, namely, the irregular character of the

some connexion between physical and chemical pheno. charcoal with which I had to deal. The experiments mena more decided than we possessed. were forgotten, I suppose, by most men, but the late Prof. Graham told me that he had repeated them with the same results that I had published. I might have considered this sufficient, but waited for time to make a still more VOLUMETRIC ESTIMATION OF SUGAR BY AN elaborate investigation of the subject, and to take special

AMMONIATED CUPRIC TEST GIVING care with oxygen, in the belief that, the rule being foundi, the rest of the inquiry would be easy; this was extended

REDUCTION WITHOUT PRECIPITATION.* to nitrogen, but not by so many experiments as with

y F. W. PAVY, M.D., F.R.S. oxygen. I am now assured of a sound foundation for inquiries, which must take their beginning from the results here given.

To be able to effect the quantitative determination of a It is found that charcoal absorbs gases in definite body with accuracy and facility is an important matter volumes, the physical action resembling the chemical. looked at in relation to the study of its bearings. In the

Calling the volume of hydrogen absorbed 1, the volume case of sugar there are no reliable means of precipitating of oxygen absorbed is 8. That is, whilst hydrogen unites and weighing it, either alone or in combination, and thus with eight times its weight of oxygen to constitute water, in the chemical estimation of this principle an indirect charcoal absorbs eight times more oxygen by volume method has to be resorted to. The only property upon than it absorbs hydrogen. No relation by volume has which dependence car be placed, for the purpose of chemibeen hitherto found the same as the relation by weight. cal quantitative analysis, is its reducing action, under the

The specific gravity of oxygen being 16 times greater influence of heat, upon certain metallic oxides, and that than hydrogen, charcoal absorbs 8 times 16, or 128 times of copper is the one which general experience shows to more oxygen by weight than it does hydrogen. This answer best. is equal to the specific gravity of oxygen squared and In the ordinary volumetric application of the copper 2. Abstract of a Paper read before the Royal Society Feb. 6, 1878.

* A Paper read at the Royal Society, January 16, 1879

of gases.


CHMMICAL NEWS, 78 Volumetric Estimation of Sugar.

February, 21, 1879. test the precipitation and diffusion of the reduced sub-, with a sufficiency of suga: to effect the complete reducoxide through the liquid interferes with the clear perception of the cupric oxide present to the state of suboxide. tion of the precise point of complete decolouration, and As the saccharine product is dropped in the blue colour thus detracts from its delicacy. For purposes where gradually fades, without any occurrence of precipitation to minute accuracy is of no moment, a sufficiently approxi- interfere with the perception of the precise moment when mate result can be obtained, but for physiological investi- the point of complete decoloration is attained. The amgation, and in other cases where precision is indispensa- monia exerts no interference with the process of reducble, the process is quite unfit for employment.

tion, but simply dissolves the reduced oxide, leading, when With the view of obtaining increased accuracy, chem complete decoloration is effected, to the production of a ists have had recourse to the plan of collecting the precipi- perfectly colourless, limpid liquid. tate of reduced suboxide and weighing it as such or after Enough ammonia must be present to secure that the reconversion into the oxide. From the difficulty, however, suboxide is held in solution, and precaution must be that exists in procuring the metallic oxide in a pure and taken that whilst the analysis is being performed the reuniform state, and from the impossibility of completely duced oxide does not become re-converted into the oxide freeing the filter paper used from adhering surplus copper by exposure to the air. To obviate this the operation solution, some uncertainty is given to the results obtained should be conducted in a flask instead of an open capsule. by this method. To obviate the difficulty here presented The appliance that naturally suggests itself as most I suggested, in a communication published in the Proc. suitable for employment is a flask of about 80 cub. centims. Roy. Soc. for June, 1877, that the precipitated suboxide capacity, with a cork inserted into the neck, through should be collected and dissolved, and the copper fre. which a delivery tube from a Mohr's burette, graduated in quently thrown down by the agency of galvanic action tenths of a cub. centim., passes for dropping in the product upon a platinum cylinder, as is now frequently done in to be examined. Through the cork, also, there must be the assaying of copper ores. The process has been found, an exit tube for the escape of air and steam from the as shown by the closeness observable in the results of Alask. Should it be desired to avoid the impregnation of counterpart analyses, to admit of the greatest precision, the surrounding atmosphere with ammonia, the exit tube and I have turned it to extensive account in some recent may be connected by vulcanised tubing with a U-shaped physiological investigations. I have conducted. In its ap: tube containing fragments of pumice stone moistened plication to such a purpose it may be held that time and with water or a wead acid. The burette being fixed in labour should be considered as of no moment, but it fre. the stand, the flask is allowed to hang suspended, so that quently happens that a more ready process of investigation there may be nothing to obstruct the full view of the conis needed than the gravimetric supplies, and on this ac. tents. The heat is applied by means of the flame of a count a volumetric method, free from the objection I have spirit-lamp, and the best position for watching the disappointed out as belonging to the ordinary plan, constitutes pearance of colour is by the light reflected from a white a desideratum.

background specially provided for the purpose. It is con. A few years back Bernard introduced, for physiological venient to have another burette, graduated in cub. centims., purposes, a modification of the ordinary volumetric pro- and of 100 cub. centims. capacity, fixed in the stand for cess, which is attended with reduction and the non-pre holding and delivering the ammoniated copper solution. cipitation of the reduced oxide. The process involves the Messrs. Griffin, of Garrick Street, have constructed an employment of a large quantity of caustic potash, and the arrangement to meet the requirements. presence in the product to be tested of extraneous organic I at first took it for granted that in the action occurring matter. Under these circumstances it happens that the the same relation existed between the amount of oxide of reduced suboxide is held in solution instead of being copper reduced and that of sugar oxidised, as under the allowed to fall, and thus decoloration without precipita- employment of the copper test in the ordinary way, viz., tion occurs and enables the point of disappearance of the that 5 atoms of oxide of copper were reduced by 1 atom colour of the test to be ascertained with precision. Ber- of sugar, and the liquid I first employed was prepared by nard, in his remarks upon the test, simply made mention adding to 100 cub. centims. of Fehling's solution 300 cub. of the fact that under these conditions reduction without centims. of strong solutions of ammonia (sp. gr. 0-880) and precipitation took place, but Dr. d'Arsonval,t his Prépa- 600 cub. centims.of distilled water. The liquid thus made rateur at the College of France, refers the effect to the contained one-tenth of Fehling's solution, and if it comsolvent influence of the extraneous organic matter in ported itself in the same manner as the latter, 10 cub. presence of the alkali.

centims. of it would stand equivalent to o‘005 grm. of grape Whilst engaged upon an enquiry into the merits of this sugar. In working with this liquid the results obtained test, the conclusion suggested itself to me that the agency were so accordant in relation to each other that I had no preventing the deposition of the suboxide was the de. misgiving about its uniformity of action; but I felt that velopment of ammonia. With an absolutely pure solu- before being definitely accepted they ought to be checked tion of sugar, such as may be obtained by inverting the against known amounts of sugar. The accomplishment ordinary crystallised cane sugar (refined loaf sugar) no of this proceeding, however, is not altogether unattended amount of potash will hinder the instantaneous precipita. with difficulty, on account of the uncertainty of obtaining tion of the suboxide. With commercial grape sugar, how grape sugar free from impurity and in a perfe&ly dried ever, and in a still more marked manner with honey, in- state. terference with precipitation is exerted, and this, I am led The method I have adopted has been to operate upon to conclude, is due to the action of the potash in producing weighed amounts of cane sugar and produce inversion by ammonia from the small quantity of nitrogenous organic boiling with an acid. I first found that the cane sugar, matter incidentally present.

which is sold in coarse colourless crystals—that which is With this before me, the idea presented itself of resort. known as “white crystal,” and used for sweetening coffee ing to the direct employment of ammonia for attaining ---stood the test on examination for purity with Laurent's the same result. It is well known to chemists that am. polarimeter. A weighed quantity was taken, and, after monia is a powerful solvent of the suboxide of copper, being inverted by boiling with hydrochloric acid, the acid leading to the production of a perfeâly colourless liquid; neutralised, and the liquid brought to a known volume, and this, from the facility with which it absorbs oxygen, subjected to treatment with the ammoniated copper liquid. quickly assumes a blue colour under exposure to air from Repeated trials were made with varying quantities, and it the re-conversion of the cuprous into the cupric oxide. was found that the results stood in harmonious relation

If ammonia be added to the ordinary Fehling's solution, to each other, but that the amount of sugar indicated was a liquid is obtained which is rendered colourless by boiling larger than the calculated amount of invert sugar from + Gazette Hebdomadaire de Medicine et de Chirurgie, September the weighed quantity of cane sugar taken.

At first I was 14, 1877, p. 454.

at a loss for an explanation of this result, but subsequent

21, ) Preparation of Single Regular Crystals.

79 observation has revealed that in the case of the ammo. | deposition of a certain amount of suboxide. Not so, howniated liquid, 6 atoms of oxide of copper are appropriated ever, with the ammoniated liquid. Here the conditions by 1 atom of sugar, instead of 5, as in that of Fehling's are such that under exposure to air the copper cannot solution used in the ordinary way. When the reckoning fail to remain in solution and to be maintained in a fully is made upon this basis the results exactly correspond oxidised state. A further advantage is given by the inwith the actual amount of sugar known ió be present. fluence of the presence of ammonia on the colour of the Moreover, with solutions of ordinary grape sugar and test, for, in proportion to the height of colour of a volu. diabetic sugar, examined comparatively with Fehling's metric liquid, so is its degree of delicacy as a reagent, and solution used in the ordinary way and the ammoniated the effect of the addition of ammonia to the ordinary copper, liquid, the results exactly accord under the copper test is to considerably increase the blue colour reckoning that 5 atoms of oxide of copper are appro- belonging to it. priated in the one case and 6 atoms in the other by 1 atom Seeing that the test here proposed acts with equal of sugar.

efficiency either in the presence or absence of extraneous To be quite satisfied upon this point, a large number of organic matter, it is alike adapted for employment by the observations under varying conditions have been made, chemist, the physiologist, and the medical practitioner in and whilst what I have stated holds good for the ammo.

relation to diabetes. niated copper liquid prepared from Fehling's solution, without any further addition of alkali, and with the addi. tion of potash to the extent of 1 grm. to 20 cub. centims. of the ammoniated test, yet a larger quantity of potash THE PREPARATION OF SINGLE REGULAR alters the action, and with 5 grms., and anything beyond, the behaviour is brought to the same as that of Fehling's

CRYSTALS OF ANY DESIRED SIZE.* solution used in the ordinary way, viz., 5 atoms only of oxide of copper are appropriated by i atom of sugar. Mr. Ferdinand Meyer, who has for thirty years studied With quantities of potash between the 1 and 5 grms., the the conditions necessary for obtaining large, single, and results stand between the 5 and 6 atoms of cupric oxide. regular crystals of chemical salts, has published his

I may mention that observation has further shown that method in the Archiv der Pharmacie, O&ober, 1878, from whilst glucose prepared from starch behaves like other which we take the following :varieties of grape sugar, there is an intermediate product Prepare a solution of any salt in water of such a formed before the completion of the process of conversion, strength that, after standing twenty-four hours, a portion which behaves in a different manner from invert sugar, of the salt will separate in crystals. Pour off the mothergrape sugar, and sugar of diabetes. Estimations made water, select a few of the best formed crystals, and place with the ammoniated copper liquid coincide with those them on a plate of glass, which lies in a rather tall vessel. made with Fehling's solution without the presence of Then re-dissolve a little of the dry salt in a small quanammonia, and the addition of potash to the ammoniated tity of the mother-water, add this supersaturated solution liquid produces no modification of the result.

to the main bulk of the mother-water, pour this upon the In order that the ammoniated copper liquid may be crystals on the plate of the glass, and place the vessel brought to the same standard of sugar value as Fehling's into a room where the temperature remains as uniform as solution, and it is desirable that this should be the case, possible, best in the cellar. The temperature of the room the proportion of copper must be increased so as to give should be ascertained by a thermometer, and in case of 6 atoms against 5: By taking 120 cub. centims. of Fehling's any changes of temperature, a further quantity of the solution, 300 cub. centims. of strong ammonia (sp. gr. sait is to be dissolved in the mother-water. This must 0:880) and making up to a litre with distilled water, the be repeated every twelve or fourteen hours, until the proper proportion is obtained, and the ammoniated liquid crystals have reached the desired size. If the solution is gives results corroborated in accuracy by the balance, and

too strong, single iegular crystals are seldom obtained at coinciding with those obtained by Fehling's solution em- once, but this is generally of no consequence, for, as long ployed in the ordinary way.

as one side at least is perfectly formed, it is only necesAs a minor point it may be remarked that the diluted sary to turn them two or three times to cause the other state presented by the ammoniated liquid offers an advan. sides likewise to become perfect. As the crystals increase tage by diminishing the liability to error arising from any in size care must be taken to give them a correct position want of absolute precision in measurement.

in the plate of glass : and, if the solution is at all concen. Twenty cub. centims. of the ammoniated copper solu- trated, the crystals must be carefully freed from adhering tion, corresponding with o‘oro grm. sugar, having been run irregularities, and then replaced in the solution. in from the burette containing the test, the flask is adapted In a solution of alum, a very oblique octoëder is usually to the cork attached to the delivery tube of the other obtained first. This may be allowed to reach a considerburette containing the saccharine product for examination. able size, after which it is to be laid successively on the The flame of a spirit-lamp is then applied underneath, narrow sides, when it will gradually become a regular and the contents of the flask brought to a state of octoëder. If it is always kept lying on the broadest sides ebullition and allowed to boil for a few minutes in order it will continue to grow obliquely. to get rid of the presence of air. The saccharine product It is well known that several isomorphous salts may be is now allowed to drop from the burette until the blue crystallised, one over the other, in layers, without a colour of the test is just removed, and a perfeály colour change of crystalline form. Chrome-alum crystals may less limpid state produced.

thus be covered with crystals of ordinary alum. The On account of the ammoniated copper solution used largest crystal of this kind obtained by the author weighed being only equivalent to 2 cub. centims. of Fehling's solu.

over three pounds. tion, it is necessary that the product to be examined

The author also observed that, when employing the should not be in too concentrated a form. For delicate same mother-water for a considerable time, the crystals observation it is convenient that the dilution should be began to show blunt or flattened points. This happened such as to require the employment of from about 10 to with regular as well as with oblique crystals, so that in 20 cub. centims. to decolourise the 20 cub. centims. of place of eight surfaces, the regular crystals gradually the ammoniated copper solution.

assumed sixteen equal sides, and the irregular ones, fourThe ammoniated copper solution enjoys the advantage teen smaller and two larger sides. If, however, the o possessing a self-preservative power. It is well known mother-water be acidulated with a little sulphuric acid, in the case of Fehling's solution that, in the course of this flattening of the point occurs but rarely. time, not only does the liquid become impaired in stability, but actually reduced in strength, by the spontaneous

* F:om“New Remedies," Janary, 1879.


I. 2.




In a

Phos. of


Analysis of Bleaching-Powder.

{ February 21, 1879

, As a general rule, this changing the position of the , become apparent that the attempt to fix upon a standard single crystals of any salt, but particularly of sulphate of must be abandoned, and perhaps some experiments made zinc, copper, nickel, or magnesium, and of Rochelle salts, by me last April and May, may assist to throw more light different forms of the same system are obtained. If crys- on the question. tals of Rochelle salt, which may easily be obtained of

TABLE I. large size, are always placed upon one and the same side, onehalf of the crystal will become perfectly developed ;

Six Samples of Flour. but if they are laid, alternately, upon the two opposite

Grains per 4 lbs. long surfaces, the development is less regular. On placing

Alumina expressed

Siliccoug large crystals of the same salt, even if only half developed,

as Alum.

Matter. lengthwise into the liquid, alternately upon either end,


5'47 development of the lateral surfaces proceeds very regu.


55'00 larly.


56.00 It is not advisable to introduce crystals into a solution


40'00 if the latter is at all warm, or to pour a warm solution


30'00 into a cold one containing crystals, as the latter are

477 thereby generally torn or broken. If a portion of a crystal has been by accident broken off, it may be repaired In the first table are the analyses of six pure flours. I by subjecting it to the above-detailed process. was satisfied that they were quite free from alum, and yet crystal of chrome alum, from which a piece weighing ten I found alumina equal in No. 1 equal to 24-30 grs. of alum per grms. had been broken off, the gap was completely re- 4 lbs. stored by subjecting it to the feeding process for a fort. The first four flours came from a large mill where much night.

foreign grain is used, and No. 6 was made at a small As soon as the crystals have attained the desired size country mill from English grown wheat alone. It occurred it is best to place them into less concentrated solutions, to me that the quantity of alumina in flour might depend in a slightly cooler place; this after-treatment causes the on the variety of grain from which it was prepared ; and surfaces to become smooth and levelled, and the edges to with a view to ascertain if such were the case, I made become sharp.-Pharmaceutical Journal.

several analyses of wheats from different countries, and have tabulated the results.


Milligrms. per 100 grms.

Phos, of Siliceous
Variety of Wheat.

Being requested some time ago to make an analysis of



18:10 164.00 an unsatisfactory sample of commercial bleaching-powder,


21'00 15:16 184'00 and finding it to absorb moisture very rapidly, I made the



20:00 170'00 following experiments, which I think might interest your


27:20 34'00 206'00 readers.



36'00 226'00 The rate of absorption was determined by exposing 6. Russian

17:20 20'00 Ior'00 100 grs. to the atmosphere of the laboratory and weighing 7


24:45 17:20 131'00 every two hours during the day.

8. Ditto

13:10 II'40

70'00 In 24 hours it absorbed 25 per cent of moisture.


16'35 16:34 126.00


4'00 9'00 48.00 72 52-3

Oregon ..

4'00 8:11 36.00 English

5'12 7:40 35.00 69



40'00 14: Ditto

730 14'00 30'00 A small quantity now left is in a liquid condition.



4970 32'00 The sample was sold as containing 35 per cent of

16. Stetin

16:33 26.40 Tog'00 available chlorine, but was found to only contain 28:6 per


13:24 21:23 cent. Its percentage composition was :

18. California


31'00 Calcium..



II varieties mixed 15'10 12:30 59'00

Egyptian asimptd. 167.00

370'00 Difference (oxygen, &c.)


Ditto, hand picked 49:49 27.20 117'00

Ditto, washed .. 14:10

100'00 The calcium was determined as carbonate, and the

Nos. 1, 2, 3 are Calcutta wheats, now largely imported total chlorine as chloride of silver.

and much prized by millers. The following six refer to Russian wheat. The Kourish variety is particularly high in alumina and silica. Nos. 10 and 11, and the English

wheats, Nos. 12 to 15, are very much alike. No. 18 was ALUM IN FLOUR AND BREAD.

a sample of Californian wheat, a pretty looking, large,

white grain, remarkably low in alumina and iron oxide. By M. D. PENNEY, F.C.S.

No. 19 was a mixture of 11 varieties mixed by a miller

preparatory to grinding. Egyptian wheat, as imported, The quantity of alumina naturally present in pure flour is much intermixed with clay. It seems that the lighters and bread has been a subject of discussion for many years, in which it is carried on the Nile are unprovided with and has been erroneously assumed by some chemists not to hatches, and in lieu of them the cargo is covered with exceed an amount equal to 8 or 10 grains of alum per 4 lbs. mud, which is soon baked hard in the sun and gives a At a meeting of the Society of Public Analysts, February 5, firm footing to the boatmen. This rough treatment 1875, it was stated by one speaker to be as low as 2 grs., accounts, no doubt, for its presence in the form of dust, and by others as high as 10 grs., expressed as alum per pellets, and lumps. It is always more or less cleansed 4 lbs. of bread; and a rather prominent analyst asserted preparatory to grinding; but it does not appear practicable, at the “ Selby case” a few months ago that, in his opinion, with the cleansing apparatus attached to the best con2 grs. were quite sufficient to allow for. It has recently structed mills, to get rid of all the extraneous matter in


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February 21, 1879.
Some Complex Oxides of Cobalt and Nickel.

81 grain. Sometimes the holes made by the weevil (an in- | boiled for about half an hour. I found that by this process, sect infesting some kinds of wheat, Calcutta for instance) | it is easy to destroy all matter, except the oxide, are filled with dirt, and no amount of working or screening capable of liberating iodine on treatment with potassic will extract it.

iodide and hydrochloric acid. The solution having A glance at the table will show what kind of flour to been cooled, it was mixed with excese of potassic expect from any of the wheats. It is rarely, however, that iodide, and then with enough hydrochloric acid to dissolve any one kind is ground by itself. It is the practice of the suspended oxide. The liberated iodine was then millers to mix several kinds, and the mixture varies in estimated by a standard solutiou of sodic thiosulphate every mill and in every part of the county according to (Na2S2O3). the supply of foreign grain and the quality of our home- In the first experiments I used a standard solution of grown.

nitrate of nickel, and calculated the nickel from the iodine No. II. Table shows that some varieties of wheat are set free according to the following equation :-more contaminated than others with alumina. I use the

Ni203+6HCI=2NiCla+Cl2+3H20. word contaminated advisedly, as I believe that the greater portion of it is due to extraneous matter, and it reveals

The results were not satisfactory, as will be seen from the source of the excessive quantity of alumina occasion. the following Table:ally met with in flour.

Nickel used.

Nickel found. Since it is impossible to fix upon a standard of natural


Grm. alumina, and since it is erroneous to regard its amount,


0'1437 even in the presence of alum, as in any degree a measure


0'1580 of alum, it may be asked—What is the use of estimating


O‘1465 it at all ?


0:1568 I venture to suggest that it might indicate whether the


0:1639 grain was or was not cleansed properly before grinding ;


O‘1541 but the estimation of silica would answer just as well.

Besides these analyses there were several which yielded Experience will enable us, perhaps, to decide on the limit to allow for clay in flour. If a line were drawn somewhere applid to cobalt, with this difference, that the solution

a far less quantity of nickel. The same method was then it would probably make millers more careful in the cleansing was boiled only for a few minutes, as I found that length process.

Dr. Dupré's “chloroform ” method of separating alum of time sufficient for the decomposition of the last traces from flour appears from his reports to be satisfactory:,,A much greater than would be due to the oxide Co203, while

of hypochlorite. The amounts of iodine liberated were correct quantitative test for alum in bread is still a desideratum. As for a qualitative test, there cannot be they agreed perfectly with an oxide Co30s, thus:anything more simple and certain than the logwood test

Cobalt used. Iodine liberated. Theory of Iodine properly applied. I have tried it repeatedly with different

for Cogos kinds of four and bread, and never found it to fail. It


Grm. does not matter, in my opinion, whether the solution is


0'5343 new or old, and all the logwood chips I have come across

0:1865 0-5380

05343 answer well. I have never found any difficulty in distin

0'1865 0.5328

O'5343 guishing the alum colour from that caused by soil, mag

I now repeated the experiments with nickel, taking care nesia, or any probable constituents of flour or bread. "I

to boil the liquid only a minute or two. In one or two therefore place implicit trust in it, and feel rather surprised instances it was not boiled, but the precipitate filtered off that its efficiency is sometimes questioned.

and washed. The results were as follows:Hull, January 31, 1879.

Nickel used. Iodine liberated. Theory of Iodine

for Nigos.







By THOMAS BAYLEY, Assoc. Royal Coll. of Science, Ireland. With a mixture of o'1863 grm. cobalt, and o'1835 grm.
Demonstrator of Pratical Chemistry, Analysis, and Assaying in the nickel :-
Mining School, Bristol.

Iodine found.

Theory for Iodine due

to N ,O, & Co,O3. Grms.

Grms. While preparing standard solutions of nickel and cobalt salts for the purposes of a research on the colorimetric


I'0627 relations and on the colorimetric estimation of those metals, In the last cases the oxides were not boiled, but the I was endeavouring to use a modification of the method of solution was allowed to stand over the steam bath for a few estimating nickel and cobalt, indicated by Bunsent, hours. depending for their determination on the iodine liberated

With solutions of known 'quantities of nickel I now by the higher oxides of these metals in contact with hydro made the following experiments. The solution with the chloric acid and potassium iodide.. The method was as suspended oxide was boiled for some hours. follows:—The solution of the nickel or cobalt salts was

Nickel used. lodine found. Theory of Iodine made alkaline by soda and then mixed with excess of sodic

for Nigo, hypochlorite obtain by the action of cold dilute sodic car

Grm. bonate on fresh bleaching-powder.


0:2642 After allowing the slightly warm solution of nickel or


O'2642 cobalt to stand some time, so as to ensure complete oxida

0:1835 0'2321

0-2642 tion, the temperature was raised until brisk effervesence


0-2642 ensued, and the solution allowed to remain at that tem


0'2642 perature until the excess of hypochlorite was decomposed.

Oʻ1835 0:3765

0'2642 When the evolution of oxygen had ceased, the liquid was

0:1835 O‘1069

0'2642 • A Paper read before the Royal Irish Academy, June 25, 1877.

In the last experiment the solution was builed for a t Ann. Ch. Pharm., 1xxxvi., 265.

few days.





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