282

grms. are dissolved, and 9 if the acid is prepared at 99'5 per cent. If nitrous compounds are present the amount of metal dissolved is in much larger proportion. Platinum alloyed with iridium is much less attacked, an advantage, however, which is, to a great extent, compensated by the brittleness of the alloy.

New Alkaloid, Ergotinin, found in the Ergot of Rye.-M. Ch. Tanret.-This compound is a fixed solid, exists only in very small amount, and is very readily affected by the air, which renders its extraction difficult. Like all the alkaloids it has a decided alkaline reaction, and saturates acids. It yields precipitates with the double iodides of mercury and potassium, with the ioduretted iodide of potassium, phospho-molybdic acid, tannin, chloride of gold, chloride of platinum, and bromine water. Its most striking reaction is the colour which it gives with moderately concentrated sulphuric acid-a yellowish red,

which becomes an intense violet-blue. If it has been exposed to the air for some minutes it loses its distinctness, and finally is no longer produced. Its saline solutions, on exposure to the air, quickly become rose coloured, and then red. If the extractive liquor is distilled with a concentrated solution of soda or potassa, mere traces of the alkaloid are obtained, but, instead, a large amount of methylamin-doubtless a product of its decomposition. In another experiment, where the liquid had been submitted to prolonged evaporation in the air, nothing but ammonia was obtained, all the alkaloid having disappeared. The great instability of this alkaloid may explain the rapid alteration of the powder of ergotised rye.

Les Mondes, Revue Hebdomadaire des Sciences,
No. 11, November 11, 1875.

This issue contains no chemical or physical matter except what has been already noticed elsewhere.

No. 12, November 18, 1875.

This issue contains a notice of an establishment at New York for preserving fish, &c., by cold.

M. Schroeder, of Baltimore, proposes to convey the American mails to Hamburg, Paris, and Lisbon in six days. He hopes to effect this by means of an invention for steering balloons, and which is to enable him to cross the Atlantic in fifty hours.

M. Toselli has made great improvements in diving-bells and in machines for grappling and raising objects from the bottom of the sea. He makes use of a powerful electric lamp. When this lamp is in action multitudes of fishes of all sizes collect around it. M. Toselli proposes, as a new kind of fishery, to kill them by the explosion of a torpedo. (We presume the torpedo will have the discretion not to damage the electric lamp.)

Two projects are put forward for dealing with the sewage of Paris. The one proposes to extend the conduits of Gennevilliers to the forest of St. Germain, and increase the surface of land to be irrigated. The other is to construct, at the expense of 70 to 80 million francs, a special canal conveying the sewage to the sea. The latter scheme is strongly supported by the Municipal Council.

M. Reimann's Färber Zeitung,
No. 43, 1875.

This issue contains receipts for a green and a grey on half-woollen goods; for dyeing and finishing blue shirtings; and for printing a puce, red, and rose (garancin style).

No. 44. 1875.

MISCELLANEOUS.

CHEMICAL NEWS, Dec. 10, 1875

Prof. Alfred H. Garrod. Twelve Lectures on the "Classification of Vertebrated Animals." On Tuesdays, Jan. 18 to April 4.

Prof. Gladstone, F.R.S.-Eight Lectures on the "Chemistry of the Non-Metallic Elements." On Thursdays, Jan. 20 to March 9.

Wm. Spottiswoode, Esq., LL.D., Treas. R.S., Sec. R.I. Four Lectures on "Polarised Light." On Thursdays, March 16 to April 6.

R. P. Pullan, Esq., M.R.I.B.A.-Three Lectures on his "Excavations in Asia Minor." On Saturdays, Jan. 22, and Feb. 5.

29,

W. T. Thiselton Dyer, M.A., B.Sc., F.L.S., AssistantDirector, Royal Gardens, Kew.-Four Lectures on the 'Vegetable Kingdom; the Boundaries and Connections of its Larger Groups." On Saturdays, February 12 to March 4.

Prof. G. Croom Robertson, M.A.-Three Lectures on the "Human Senses." On Saturdays, March 11, 18, and 25. Edward Dannreuther, Esq.-Two Lectures on "Wagner and his Trilogy," with pianoforte illustrations. On Saturdays, April 1 and 8.

The Friday Evening Meetings will begin on January 21, 1876, at 8 o'clock; the Discourse by Prof. Tyndall, at 9 p.m. The succeeding Discourses will probably be given by Prof. Huxley, Mr. W. Preece, Mr. Wm. Crookes, Dr. C. W. Siemens, Lord Lindsay, Earl Stanhope, Prof. W. H. Flower, Sir H. S. Maine, Prof. Odling, Mr. E. B. Tylor, and Prof. James Dewar. To these meetings

Members and their friends only are admitted. University of London.-The following is a list of the candidates who have passed the recent B.Sc. Examination for Honours :

Mathematics and Natural Philosophy (B.A. and B.Sc. conjointly).-First Class: R. C. Rowe, B.A. (Scholarship), Trinity College, Cambridge; H. F. Morley, B. A., University College. Second Class: W. H. Bennett, B.A., Lanc. Indep. and Owens Coll.

Chemistry (B.Sc. only).-First Class: J. M. H. Munro, Royal Coll. of Science, Dublin; A. J. Smith, Owens College; S. P. Thompson, B.A., Royal School of Mines. Third Class: F. A. Cooper, Owens and University Colleges; J. E. Harris, B.A., private study; C. M. Thompson, University College.

NOTES AND QUERIES.

Coal-Tar.-A Subscriber will be glad to be informed of the best and most recent authority on the chemistry and distillation of coaltars, showing the character, boiling-points, and specific gravity of the various products.

Magnesia Bricks.-Can you or any of your readers inform me where and how magnesia bricks are made, or where I can get informa tion on the subject?-P. D.

TO CORRESPONDENTS.

Inquirer. (1) Angell and Hehner's" Butter; its Analysis and Adulterations" is published by Daldy, Isbister, and Co., 56, Ludgate Hill, E.C. (2) Suffolk's "Microscopical Manipulation," price 38. 6d., pub

VOL. XXXII. No. 838.

ON THE ESTIMATION OF ARSENIC 'AS MAGNESIUM AMMONIUM ARSENIATE AND AS MAGNESIUM PYRO-ARSENIATE.

By R. W. EMERSON MACIVOR, F.C.S.,
Mem. Phys. Soc. Lond.

THE present communication contains an account of a series of experiments on the methods of Levol and Rose for estimating arsenic. I was induced to take the matter up from the circumstance of my having been compelled to reject Levol's process, on account of its yielding low results, while engaged in making some accurate determinations of arsenic. I was subsequently led to study Rose's method.

Levol's Method: Determination as Magnesium Ammonium Arseniate. This process, as commonly recommended in analytical handbooks, may be briefly described as follows:-The arsenic, after separation from other metals, is obtained in solution as arsenic acid, and then converted into ammonium arseniate by the addition of excess of ammonia. A solution of magnesium sulphate, containing sufficient ammonium chloride to prevent the precipitation of magnesium hydrate, is next added, and the whole allowed to stand for about twelve hours, so as to render the precipitation of the arsenic complete. The MgNH4AsO4+6H2O is collected on a tared filter, washed

with dilute ammonia, dried in an air-chamber at a temperature of 105° to 110° C. until weight becomes constant, when the dried precipitate is assumed to have a composition represented by the formula 2MgNH4AsO4+Ĥ2O. Regarding the reliability of this method, chemists express diverse opinions. Some, as Fresenius, Field, Wittstein, and Puller, consider it reliable, while others again, as Rammelsberg and Parnell, condemn it as yielding only approximate results. For my own part I share the opinion of the last named chemists. As already mentioned, I obtained low results with the process, and was consequently led to doubt the correctness of the formula assigned to the arseniate as expressing its composition after drying at 110°. A number of experiments on the effect of different temperatures on the salt were accordingly

made.

13050 dried at 105° to 107° lost o°4943 grm.=37.88 per 1'4550 grm. by drying at 100° lost 0.5439 grm.=37:38 per

cent.

10820 lost 0 3682 grm. =34'05 per cent. after about twenty hours' heating at 95°.

Assuming 2MgNH4AsO4+6H2O to lose 11 molecules of water by drying at 105° to 110°, the total theoretical loss would be 34'25 per cent.-a number much below that actually found. If we, however, assume, with Field, that the salt loses the whole of its six molecules of water, the percentage loss rises to 37'37. This number is considerably lower than the loss found to take place at 105° to 110°, but agrees very well with that taking place at 100°. Field's view, however, is untenable, since I found ammonia to be expelled from the arseniate at a temperature somewhat below 100°.

In order to determine the quantity of ammonia given off at 105° to 110° the following experiment was made :A weighed quantity of arseniate was introduced into a tube, so arranged that it could be kept at any required temperature, and connected at one extremity with a U-shaped tube containing dilute hydrochloric acid, and which in its turn was attached to an aspirator, by means of which a slow current of air was maintained passing through the tubes. The tube containing the arseniate was heated to 105° to 110° for about two hours, when the contents of the U tube were transferred to a porcelain basin, and the ammonium choride determined with platinum tetrachloride. The platinumn-ammonium choride was, by ignition, converted into metallic platinum, which was then weighed. 20514 grm. MgNH4AsO4+6H2O gave 10464 grms. Pt=0'0903 NH3=4'4 per cent.

From the above results I draw the conclusion that Levol's method-as commonly recommended in textbooks-can only yield approximate results.

Before concluding this portion of my paper I may mention that the expulsion of ammonia from the double arseniate was first noticed by E. W. Parnell, and more recently by Rammelsberg. It is now almost two years since I first made the observation in the laboratory of Professor G. Bischoff and, consequently, long prior to the publication of Rammelsberg's paper, and I was not aware of the fact having been already established until my attention was drawn to Parnell's paper by Dr. W. Ramsay.

Rose's Method: Determination as Magnesium Pyroarseniate. As in the case of Levol's process, diversity of opinion exists regarding the validity of this method. It is upheld by Levol, Rammelsberg, Thorpe, Puller, and Wittstein, and condemned by Fresenius and Parnell. My experiments fully confirm the excellence of the process. I do not, however, find it necessary to observe many of the precautions recommended by Puller, Wittstein, and others. My mode of working the process is as follows:

The double arseniate is dried at 120°, introduced into a porcelain crucible and heated in an air-bath first at about 140°, and afterwards at 180°, then over a Bunsen burner, the flame of which is slowly raised, and finally finishing over the blowpipe.

Scientific Chemical Laboratory,
Andersonian University, Glasgow.

vision for the destruction or neutralisation of the offensive vapours. Occasionally the operations are conducted in closed iron cylinders set vertically; so that the charge may be dropped into them at the top and let out at the bottom. When full they are made tight and submitted to the action of high pressure steam (from 30 to 50 lbs.), which is blown into them for ten or twelve hours. In this manner the materials are perfectly disintegrated, and after standing for a few hours to cool the liquid portion, consisting of water and fat, are first run out through a tap at the bottom, and then the solid parts are removed. Apparatus of this kind can be worked without annoyance to the neighbourhood; but if the manufacturer prefers to mix his materials in his own way, it should be done in a close chamber or cylinder with revolving arms, and with a contrivance for carrying the offensive gases to the furnace fire. Other operations, as fish drying and smoking, and the preparation of albumen from blood and eggs, also deserve notice as requiring attention and cleanliness to guard against nuisances.

Animal Charcoal Burning.-This until lately was a great annoyance to the inhabitants of the neighbourhood in which sugar bakers reside. Formerly the bones were burnt in iron retorts set in a furnace without much precaution against the escape of the offensive empyreumatic vapours; and the red-hot charcoal was cooled and quenched in iron boxes by means of water, whereby much sulphuretted hydrogen was evolved. The processes, however, at present in practice are planned with every consideration for the public comfort. The retorts are so constructed that the vapours from the ignited bones are carefully conducted to the furnace-fire and are burnt; and the red-hot bone black is received into specially designed coolers that do not permit of the access of atmospheric air, which would be destructive of the carbon of the bones. When the animal charcoal has become exhausted of its decolourising power, it is again burnt and revivified in revolving retorts, or in well-designed vertical cylinders, which do not permit of the escape of any offensive matter into the surrounding atmosphere, but discharge it into the furnace-fire.

The roasting of coffee, chicory, and cocoa, if not properly managed, is offensive. The operation is performed in a revolving cylinder or cage set over a coke or charcoal-fire enclosed in a tight chamber, which is ventilated to the chimney shaft. In the case of coffee and cocoa the roasting operation is often performed in wire cylinders; whereas that of chicory, on account of the large quantity of powder produced, is always of sheet-iron. The cylinders are about 4 feet long and 20 inches in diameter. They receive about a hundredweight at a charge, and they are run into the roasting chamber upon a square axle, which supports them over a clear fire about a foot above it. They are then set in gear, and turned by machinery at the rate of about fifty revolutions a minute. There are breaks in the interior of the cylinder to distribute the coffee or chicory during the roasting so as to equalise the action. The operation lasts about thirty or thirty-five minutes for coffee or chicory, and half the time for cocoa; and the empyreumatic vapours go into the fire and up the chimney shaft. When the operation is finished, in the case of coffee and cocoa, the roasted berries are cooled by a blast of air, and this blows about a quantity of the outer covering of the coffee berry (called flights), which are occasionally annoying to the neighbourhood. The loss of weight during these operations is from 14 to 16 per cent for coffee, from 9 to 11 per cent for cocoa, and about 25 per cent for chicory. Brown malt and roasted corn are likewise roasted in much the same manner, and require that the empyreumatic vapours should be carried into the fire and be burnt.

There is another vegetable matter which in burning has lately caused offence to the neighbourhood in which the operations are conducted. This is the resinous matter obtained by the evaporation of the alkaline liquor obtained in the treatment of Esparto grass and straw in paper

making. The liquor is first evaporated in large close evaporating pans, which receive the full force of the fire above and below, and thus the vapours are carried forward into the chimney shaft. When the residuum is sufficiently consolidated it is roasted in a furnace for the pupose of burning off the organic matter and recovering the alkali. This operation has been forced upon the paper-makers in consequence of the difficulty of disposing of the spent liquors. The residuum of the evaporation would no doubt serve as a means of preventing scale or fur in steam boilers.

Within the last ten years a new branch of industry has sprung up in this country on account of the permission to use sugar as well as malt in the production of beer. The sugar is called saccharine, or glucose, or grape sugar, and it is generally made from the cheapest and most accessible kinds of starch. Rice starch is that which is commonly used in this country at the present time. The rice is crushed between rollers and macerated in a vat with a little alkali for about twelve hours, during which time it is constantly stirred by revolving arms moved by machinery. In this manner the gluten of the rice is dissolved out of it, and the starch is set free. After standing quiet for about six hours the starch settles, and leaves a supernatant solution of gluten, which is generally thrown away. The starch is then transferred to another vat and treated with water acidulated with sulphuric acid About 150 lbs. of acid (sp. gr. 1·850) and 1500 gallons o water are sufficient for a ton of starch. The mixture is stirred like the last, and it emits a smell of rancid butter and grains (butyric and lactic acids). It is then run into a vertical cylinder called a " digester," where it is submitted to the action of steam, at 20-lbs. pressure, blown into it for about half an hour. This converts the starch into glucose, and the solution is allowed to flow into a vat, where it is neutralised with powdered chalk and kept stirred for about two hours, during which time the same offensive smell of butyric and lactic acids is evolved, and to a much greater extent. The clear liquor is next filtered through horsehair bags to separate sulphate of lime, after which it is evaporated in vacuo to the consistence of a very thin syrup, which is filtered through animal charcoal in the usual way. It is then further evaporated in vacuo until it looks like honey, and in this state it is poured into moulds and allowed to set. The yield of starch from the rice is as much as 80 per cent, and the yield of sugar is about 5 per cent above the weight of the starch. The saccharine or grape sugar, when well made, contains from 80 to 82 per cent of glucose, with only a trace of gum and mineral matter; and it is generally used by the brewer mixed with two parts of malt. The offensive effluvia from these operations are easily prevented by covering the vessels and ventilating them into the fire or chimney shaft. (To be continued.)

REPORT ON THE

DEVELOPMENT OF THE CHEMICAL ARTS
DURING THE LAST TEN YEARS.*
By Dr. A. W. HOFMANN.
(Continued from p. 276.)

THE three last-named methods may be considered as adapted for industrial purposes. As the peroxide of hydrogen does not solidify at 30° its solutions may be concentrated by cooling them below o°, and allowing the water to freeze out. For this purpose Houzeau makes use of the apparatus of Carre.+ A great difficulty in the

"Berichte über die Entwickelung der Chemischen Industrie Während des Letzten Jahrzehends." + Houzeau, Monit. Scient., 1868, 175.