acid. If tarry matters are present, a "gooseberry red colouration makes its appearance. [This test has been in use in dye-works, &c., in England, for at least seven years.] Identity of the Bromated Derivatives of Tetrabromic Hydride of Ethylen, and those of Perbromide of Acetylen.-Edme Bourgoin.-Already noticed.

Mutual Displacement of Acetic and Formic Acids. -H. Lescœur.-The author has never succeeded in completely decomposing a formiate by an excess of acetic acid. The reaction is not more decided with the aid of heat than in the cold. Dilution of the acetic acid diminishes the amount of formiate decomposed.

Researches on the Selenites.-M. F. Nilson.-A memoir originally published, in the English language, in the Transactions of the Royal Society of Sciences at Upsala. The author considers the results of the late Dr. Muspratt inaccurate. The selenium employed was obtained from the lead-chambers of the Fahlun Work, in which it forms about 2 per cent of the mud. M. Nilson describes selenites of potash, rubidium, cæsium, ammo. nium, thallium, sodium, lithium, and silver.

Correspondence from St. Petersburg.-M. W. Louguinine. The author briefly notices investigations by M. Schöne, on peroxide of hydrogen in the atmosphere; by M. O. Bogouch, on the formation of aldehyds; by M. N. Beketoff, on the separation of silver from nitrate of silver by the action of hydrogen; by W. Morkownikoff, on the oxidation of a-oxybutyric acid; by Beilstein, on the production of meta-dichloro-benzin by the action of nitrous acid and alcohol upon dichlor-aniline; by M. Boutlerow, on penta-methyl-ethol; by M. Boradine, on the production of dithymol by the action of chloride of iron upon thymol, and on oxydinaphthalin obtained by distilling 6-dinaphthal with anhydrous phosphoric acid.

This issue contains an article on patent law reform, in which the English patent laws are recommended for adoption in Germany.

Eosin-If this colour is stirred up with water and sodium amalgam at a gentle heat the red liquid is decolourised, and colourless fluorescin produced. If this liquid is diluted with water, and a drop of permanganate added, it becomes green and opaque by reflected light, having been converted by oxidation into fluorescein.

Gris d'Aniline or Nigrosin in Silk Dyeing.-With this colour the silk dyers produce all their greys, modes, dark blues, plum-colour, and Russian green at prices very little exceeding the wood colours. The same colour-beck can be used for days. The gris d'aniline soluble in spirit is preferable to that soluble in water, as the latter is apt to come up flat in the darker shades. The operation is performed at a boil, with soap and sulphuric acid. With the addition of orchil and young fustic are produced all conceivable shades of grey, mode, and olive green. For dark greens turmeric is added, or a combination of gris d'aniline, aniline blue, and turmeric is used. The green shades may be brightened by topping with picric acid in a fresh beck. Dark blue is obtained with gris d'aniline and aniline blue. In dissolving the colour, proceed as for other aniline colours soluble in spirit, and the solution is filtered for

This issue contains remarks on the new indigo vat; receipts for printing a green on woollen yarns and tissues; for a black on the same material; a black on felt hats; a fast light indigo blue without indigo; and for bleaching linen and cotton.

To Prevent Boiler Incrustations.-Galls, I part; glue, part; soda, part. Another authority proposes to boil 30 kilos. soda, 12 kilos. potash, and 1 kilo. catechu in 20 gallons of water, and pour the decoction into the boiler. wool and silk with it at a boil. Bang proposes to prepare soluble prussian blue, and dye

Thiré and Duport dissolve aniline colours in alcohol, mix the solution with benzol, and dye with it. A similar method can be pursued with dye-woods and astringents.

Methyl Green on Wool (50 kilos). -One-half kilo. of borax on soluble glass, 1 kilo. methyl green. Work for thirty to forty minutes at 65° R., rinse, and treat at 40' R. with 5 kilos. alum, 250 grms. bichloride of tin, and 250 gms. acetic acid. To the second dye-bath 250 to 400 grms. picric acid may be added.

Delobel proposes as a mordant for the aniline colours a mixture of sulphuric acid, turpentine, alum, and borax. Chevreuse obtains a brown dye by beheading cockchafers!

Les Mondes, Revue Hebdomadaire des Sciences. No. 12, March 25, and No. 13, April 1, 1875. These issues contain no chemical matter.

MISCELLANEOUS.

Obituary. We much regret to hear of the untimely decease, at the early age of 27, of Mr. Samuel William gical Chemistry in St. George's Hospital Medical School. Moore, L.R.C.P., F.C.S., &c., Demonstrator of Physiolo Mr. Moore had established for himself a reputation as a promising worker in the fields constituting the borderland between chemistry and physiology, his attainments in this branch having three years ago secured his election to the important post held by him in St. George's Hospital; his "Notes of Demonstrations" on this subject, subsequently published in our columns, constitute a valuable

Mr.

Contribution to chemical and medical literature. Moore's first scientific paper on "Brain Crystals" was published in the CHEMICAL NEWS when he was little more than 18 years of age; and at the time of his last illness he was engaged on a laborious series of researches on the effects of tobacco, the British Medical Association being on the point. of furnishing a considerable grant in furtherance of this object. Through the long-continued illness and premature removal of this talented student of nature, a young widow and two infant children are left wholly unprovided for and almost wholly destitute. We understand that the friends of the deceased contemplate making an appeal to the liberality of the medical profession and the scientific public with a view to raising a fund for the benefit of his family. The following gentlemen have kindly consented to form a committee for this purpose :-Dr. Barclay, St. George's Hospital; Dr. Bott,

THE CHEMICAL

VOL. XXXI. No. 811.

WITH SCHEIBLER'S APPARATUS.

By R. WARINGTON.

WISHING to ascertain whether a speedy and accurate analysis of tartar might not be accomplished by neutralising the tartar, evaporating to dryness, igniting the residue, and determining the quantity of carbonic acid in the ash, I naturally sought, in the first place, for some good and speedy method of determining carbonic acid. Scheibler's volumetric method being largely used, and well recommended, at once suggested itself as suitable for my purpose. Mr. W. E. Halse, on learning my wishes, very kindly placed a Scheibler's apparatus at my disposal. The experience gained while using the apparatus has, I think, brought to light a rather considerable error which is involved in the ordinary practice with this instrument; this point I propose now consider, reserving the results obtained with regard to tartar for a paper to be read shortly at the Chemical Society.

to

As I write for those using the apparatus, a description of the ordinary process will be unnecessary. In Scheibler's pamphlet accompanying the apparatus, instructions are first given for the determination of carbonates in bone charcoal, and afterwards the general determination of carbonic acid by means of the apparatus is described: we will consider the latter instructions first.

The carbonate to be analysed is placed in the generating bottle, and acted on by 10 c.e. of hydrochloric acid, sp. gr. 112, contained in a tube which is overturned after the bottle is closed; the gas evolved is then measured over water in the graduated tube of the apparatus. It is evident that the whole of the carbonic acid will not be evolved in the form of gas, but that some part of it will be retained in solution by the fluid in the generating bottle. Scheibler therefore directs that a correction of +0.8 measure is to be made to the volume of gas obtained. As the scale which Scheibler describes in his pamphlet is a scale of 25 measures, which is stated to be equal to 100 c.c., it is evident that the correction made is 32 c.c., and the evidence afforded by various parts of the pamphlet is overwhelming, that this is, in fact, the correction which he directs. Fresenius, however, states (fourth English edition, page 713) in his description of the process," Scheibler has determined the small amount of carbonic acid which remains dissolved in the 10 c.c. hydrochloric acid at the mean temperature, and he directs to add o'8 c.c. to the volume of the carbonic acid read off." This mistake of substituting 08 c.c. for o8 measure is again made by Mr. E. Nicholson (CHEMICAL NEWS, vol. xxix., p. 245), he says "Dr. Scheibler sets it down as o'8 c.c. for 10 c.c. of acid, sp. gr. 1'12." Mr. Nicholson, however, goes on to say that he himself employs as a correction I c.c. when using only 5 c.c. of acid, and that this correction is a little too low; Mr. Nicholson's practice is thus not very far from Scheibler's actual direction.

in the former case, and the fluid retains a much larger quantity in solution. If, therefore, a fixed correction of 32 c.c. is employed in every experiment, the result will be much too high when a small quantity of carbonic acid is produced, and much too low when a large quantity has been evolved. It was, in fact, by trying the apparatus with large and small quantities of pure carbonates that I was led to perceive the error in question.

* I quote throughout from an edition dated 1871.

Scheibler is not altogether unconscious of the source of error involved in his fixed correction of +32 c.c., for he directs (p. 24) that the quantity of the sample taken should be such that the volume of gas set free should fall between 15 and 25 measures (60-100 c.c.), as with a smaller volume of gas the correction of o8 measure is no longer constant. This important statement, which greatly diminishes the value of the process, is omitted in Fresenius, who, after describing the process as of general application, merely says "the quantity [of bone-black] taken must be such that the amount of carbonic acid obtained may not be too small; about 3 grms. of the dried substance may be considered as the correct quantity." Nicholson also gives no hint of the limitation of his correction to certain volumes of gas. It is quite evident, however, that if what has been advanced is true, the corrections both of Scheibler and Nicholson can only be strictly accurate for one volume of gas, and cannot be extended with exactness to even a limited

range.

The constant correction being shown to be erroneous, I next endeavoured, by means of test experiments with pure carbonates, to ascertain the true corrections for each volume of gas obtained. The first series of trials was made with pure anhydrous carbonate of sodium, and as it was intended in the experiments with tartar to remove the ash into the generating bottle by means of 5 c.c. of water, the carbonate of sodium was in this case also dissolved in 5 c.c. of water before being acted on by the hydrochloric acid. The total quantity of fluid in the generating bottle was thus 15 c.c., instead of the 10 c.c. supposed by Scheibler. The generating bottle was shaken in every case three minutes before reading. The results obtained were as follows. The carbonic acid is throughout expressed as cubic centimetres at 16°, and 760 m.m. pressure, saturated with water :

Carbonic Carbonate Number Carbonic Acid Correction of Sodium of Acid present required taken Experi- Evolved in (Gram). (Mean). Carbonate Experiment. of Sodium.*

in

Correction at 7 per Cent.

ments.

254

If we assume that with 15 c.c. of fluid in the bottle Scheibler's correction would be increased by one half, it will thus become 48 c.c., which will be the proper correction for some volume of gas between 60 and 70 c.c., but will be the proper correction for no other volume.

The last column in the table shows that we may assume with very little error that in the case of these experiments the correction needed is 7 per cent of the gas measured. Theoretically the correction should be a diminishing proportion with increasing quantities of gas, as the evolution of twice as much gas in one experiment as in another cannot quite double the tension of the carbonic acid in the generating bottle. It is quite possible, however, that other causes modify the result; thus the more carbonic acid is evolved, the more is the hydrochloric acid neutralised, and the liquid containing less hydrochloric acid in solution may be able to absorb more carbonic acid, and thus the diminishing increase of pressure may be counterbalanced by a corresponding rise in the solvent power of the liquid. The varying quantities of chloride of sodium present, and the heat of combination, may also affect the result.

The next series of experiments was made with Iceland spar powdered and dried; 10 c.c. of hydrochloric acid sp. gr. 1'12 were employed, and no water. The conditions were in these experiments precisely those supposed by Scheibler. Shaking was continued for two minutes in every case. The volumes of gas are reduced to the same pressure and temperature as before.

Scheibler's correction of 32 c.c. is by this table the true correction when about 50 c.c. of gas are evolved, but in no other case. We have here a smaller percentage correction than in the previous series, the quantity of fluid in the generating bottle being less; the percentage correction also diminishes somewhat with the increase of the gas evolved, which we have already seen was theoretically to be expected. The results with Iceland spar were more accordant than those with carbonate of sodium.

Two further experiments were made with carbonate of calcium, 5 c.c. of water being added as in the previous experiments with sodium carbonate. o'10 grm. of Iceland spar gave 22.22 c.c. of gas, reduced to 16°, and 760 m.m.; the correction required was therefore 174 c.c., or 7.83 per cent. With o'40 grm. of spar, 89.19 c.c. of gas were obtained, requiring a correction of 6.67 c.c., or 7'47 per

cent.

We now turn to the first part of Scheibler's pamphlet, in which he gives instructions for the determination of carbonate of calcium in bone charcoal. Here the volume of gas found is not corrected by the addition of o-8 measure, but 17 grms. of charcoal having been taken for the determination, the percentage of carbonate of calcium is at once found by referring to Table I., in which to every measure of gas found is assigned its value in percentage of carbonate of calcium. The accuracy of this table can be easily examined by means of the test experiments with calcium carbonate just quoted; we have only to imagine that in each of these experiments 17 grms. of charcoal was taken, containing the quantities of carbonate of calcium actually operated on, and compare the percentage of carbonate of calcium present

{CHEMICAL NEWS,

June 1875.

It is clear from these figures that the percentages of carbonate of calcium deduced from Scheibler's Table I. are too low, and that the error is somewhat serious. I confess I do not understand how Table I. has been calculated, especially how in any part of the scale a measure of gas can have a smailer value than the amount of carbonic acid it contains; this is, however, actually the case in a part of Scheibler's table.

Scheibler's apparatus is one of great practical value, as very speedy results of fair accuracy can be obtained by its use. The mode of calculating the results described by Scheibler must, however, be abandoned, so far as the use of a fixed correction for the retention of gas in the fluid, and the employment of Table I. is concerned. By substituting a correction proportional to the volume of gas obtained, and reducing the volume of gas into terms of the carbonate sought by means of Scheibler's Tables III.-VI., the errors hitherto made will be avoided. I do not at all pretend that the proportional corrections here given as the result of my own experiments will be found to hold good at all temperatures, they are probably strictly true only for the temperature of the experiment.* A far more complete series of observations is required.

There are one or two points connected with the use of the apparatus which I will in conclusion briefly mention. Any rise of temperature during the experiment entails a notable error, as the final reading is increased by the expansion of the whole volume of gas in the apparatus. A small rise in temperature is sure to take place if the operator stands before the instrument for two or three minutes while shaking the generating bottle. This inay be avoided by placing a narrow glazed screen between the instrument and the operator. should also be wrapped in paper during the agitation. The generating bottle Bone charcoal, and many other substances in which carbonic acid has to be determined, contain small quantities of sulphides; to prevent sulphuretted hydrogen being evolved a small quantity of mercuric chloride may be dissolved in the hydrochloric acid used.

ACTION OF CHLORINE ON PYROGALLOL.* By JOHN STENHOUSE, LL.D., F.R.S., and CHAS. E. GROVES. THE authors, after noticing the unsatisfactory results which they obtained by acting on pyrogallol in aqueous solution, proceed to describe the phenomena which take place when a current of chlorine is passed through a mixture of pyrogallol with twice its weight of glacial acetic acid.

At first, the liquid, which should be kept cool, assumes a dark, inky, purple colour, and occasionally deposits crystals of pyrogallol, thrown down by the hydrochloric acid produced in the reaction. As the action proceeds, however, these dissolve, and at last, when saturated with chlorine, the solution becomes of a pale orange red. If it be now heated to 70° C. for a short time, carbonic anhydride and hydrochloric acid are given off, and on cooling brilliant crystals of mairogallol are deposited.

Mairogallol, C18H,Cl11O10, forms hard colourless sixsided prisms, which are insoluble in water, but very

The temperatures during the test experiments varied from 15° to 18° C. Abstract of a Paper read before the Chemical Society. From μarpe, obs. to glitter.