"The small number of phosphatic calculi included in this last list, confirms the opinion, previously expressed, that the phosphates are chiefly deposited as an external coating on calculi of large size.

"Having, in the preceding section, treated generally of the physical, as well as chemical properties of vesical calculi, I shall now proceed to classify them, and to give more detailed instructions for the separation and examination of their various constituents.

"The classification I propose, is founded on the changes which are produced on calculous concretions, by exposing them to a high temperature.

The effect first produced on a fragment exposed to the blow-pipe flame is, that it becomes charred, owing to the combustion of the animal matter calculi always contain. "If the heat be continued, or augmented, one of the following conditions is fulfilled :"1st. The fragment gradually consumes, leaving no residuum, or a very slight one. "2nd: The fragment does not consume; it either whitens after being charred, and remains unchanged, or it fuses into a bead.

"3rd. The fragment partially consumes, leaving a considerable proportion of residuum.

"These obvious differences of behaviour,

"Woode Collectionibus Scholæ in Windmill Street, Conditæ. Lond. Med. and Phys. Journal, No. LVII. p. 29, January 1827."

1 : 2.2 1: 3.33

1 (115) 1.21

:

=

1 : 10.89

1: 10.1 1: 1.87 1: 15

under parallel circumstances, naturally suggest the division of calculi into three classes.

"CLASS 1st. COMBUSTIBLE CALCULI, which consume on being sufficiently heated, leaving a very minute residuum.

"CLASS 2nd. NON-COMBUSTIBLE CALCULI, which do not dissipate under calcination.

"CLASS 3rd. PARTIALLY COMBUSTIBLE CALCULI, which, after combustion, leave a considerable proportion of residuum.

"The 1st Class includes the following orders:

a. Uric acid.

b. Uric oxide. c. Cystine.

d. Combinations of the three preceding, with each other, or with other combustible materials, such as ammonia, &c. "The 2nd Class includes the following orders :—

a. Phosphates.

b. Carbonates.

c. Silica.

d. Mixtures of the preceding.

"The 3rd Class includes the following orders, namely, compound calculi formed by the combination of the species contained in the two former classes.

a. The residuum consisting of the phosphates.

b. The residuum consisting of carbonate, or caustic bases.

c. The residuum consisting of phosphates, with carbonate or caustic bases.

d. The residuum consisting of accidental ingredients, either alone, or mixed with the foregoing.

"The objection 'urged against this sort of arrangement is, the necessity it involves, for having recourse to experiments, for the mere purpose of classing the calculus. But, it should be remembered, that if accuracy is desirable, chemical investigation must, ultimately, be resorted to; these simple experiments, therefore, are not only so

OTLEY,

SERVATIONS MADE AT YORKSHIRE, IN FEBRUARY, 1843.

"It would certainly be more speedy and more convenient, if a useful classification could be framed, from the aspect of calculi alone; but as this does not denote their internal structure, the most accurate inspection, although it may aid, can never supersede chemical examination."

LITERARY ANNOUNCEMENT.

WE are glad to find that a Journal devoted to Dental Surgery is to be published on the 1st of April. It is edited by Mr. ROBINSON, who has long been known to the profession as a lecturer and operator. Conducted by one so well fitted by his pursuits for the task, the Quarterly Journal of Dental Surgery cannot fail to arrive at a considerable circulation among scientific dentists, medical practitioners, and chemists, many of whom practise as dentists.

TO CORRESPONDENTS. "J. R. C., MANCHESTER."-We will write to you, with what you require.

"A SUBSCRIBER FROM THE COMMENCEMENT," who inquires of us respecting Alpacas, and the adulteration of Guano, had best give us his address, that we may write to him privately.

"A READER."-We could better answer you by letter.

NUMEROUS CORRESPONDENTS who write to us on the subject of the Charter of the Pharmaceutical Society, are informed, that they have nothing to apprehend from not joining the Society. If they belong to it, they will lose their money; if they do not, they will save their money and lose nothing else.

"A. B."-You are wrong. "X. Y. Z."-Decidedly not. "AN OLD CORRESPONDENT."-We recommend the use of the native sulphuret. "DR. R--" shall hear from us privately, before the 10th of April, with the information he requires.

"A TRANSATLANTIC SUBSCRIBER" will observe our answer in the next No.

"R. S."-Why? write and tell us; will help you.

we

"A SUBSCRIBER, Dublin."-Not that we are aware; however, we will be on our guard.

ERRATUM in No. XXXIX.

In the Review of Dr. Willis on Stone, page 140, col. 1, line 28 from the bottom, for Chemical Means," read" Mechanical Means."

BY. E. THOMPSON.

ON SOME SEPARATIONS OPERATED BY MEANS OF SULPHUROUS ACID OR THE ALKALINE SULPHITES.*

BY M. P. BERTHIER.

SULPHUROUS acid and the alkaline sulphites have long been employed with advantage in many docimastic operations. I have myself pointed out some of their uses, and have shown particularly: 1. That by means of sulphurous acid, oxides of zirconium and titanium are easily procured perfectly pure, notwithstanding the difficulty of removing the last traces of iron: 2. That chrome may easily be separated from iron, and alumina from glucina, &c.; and on this occasion, I have investigated the action of sulphurous acid on the most common metallic sulphurets, and on some oxides. I have since found that this reagent, whether free, or in the state of combination with alkalis, was susceptible of new applications, which appear to me capable of simplifying many analytical operations. I am about to make known these applications, first succinctly indicating the properties of the principal sulphites.

The sulphites of baryta and strontia are almost insoluble in water, and very sparingly soluble in sulphurous acid.

Sulphurous acid easily dissolves even native carbonate of lime. Sulphite of lime is scarcely more soluble in water than the sulphate; it dissolves in great quantity in sulphurous acid; but when the solution is boiled, the greater part separates in the state of granular crystals.

Calcined magnesia easily dissolves in sulphurous acid, even without heat; the liquor does not become turbid by boiling, and if it be heated or spontaneously evaporated, it furnishes transparent prismatic crystals of sulphite.

Yttria, in the state of hydrate or carbonate, dissolves in sulphurous acid, and the solutions of its salts are not rendered turbid, cold, by the alkaline sulphites; but if they be boiled, the whole of the earth is precipitated in the state of subsulphite completely insoluble in water, but soluble in sulphurous acid.

Glucina acts with sulphurous acid like magnesia, and its solutions are not rendered turbid by boiling.

Alumina dissolves in sulphurous acid, but only when it is in the state of humid hydrate; it is afterwards completely precipitated from the liquor by boiling, and the deposit is a hydrate and not a subsulphite. This hydrate is gelatinous, easy to filter and wash, and, after it is dried, it is pulverulent, opaque, and of a fine white. The alkaline sulphites supersaturated with acid do not render the salts of alumina turbid, without heat, but, when boiled, all the earth is separated. When an excess of ammonia is poured into a solution of sulphite of alumina, a considerable portion of the earth at first precipitated is redissolved; but the dissolved portion is again precipitated by boiling.

When a solution of phosphate of alumina is boiled with sulphite of ammonia, all the phosphate is precipitated. But if a solution of arseniate of alumina be treated in. the same manner, only perfectly pure alumina is precipitated, and all the arsenic remains in the liquor in the state of arsenious acid.

Zirconium and titanic acid dissolve only in very small quantity in sulphurous acid, and the dissolved portion entirely separates from the liquor by boiling. The solutions of zirconium and titanium are not rendered turbid, without heat, by sulphite of ammonia; but when boiled until there is no longer any odor of sulphurous acid, the two oxides are completely precipitated; they are both then easy to filter, and, after

† Annales de Chimie, tome LI. p. 191. N.S. VOL. I.-No. V. May, 1843.

they do not retain a perceptible quantity of sulphurous acid.

2 C

The ammoniacal carbonate of uranium readily dissolves, without heat, in sulphurous acid, and, when the liquor is boiled, all the uranium separates in the state of granular subsulphite, of a fine yellow. The yellow solutions of uranium are likewise decomposed by sulphite of ammonia by aid of ebullition; but they are not rendered turbid by that reagent, without heat.

When an excess of sulphurous acid is added to a solution of tungstate of ammonia, the latter undergoes no alteration; and if the liquor be supersaturated with sulphuric acid, the tungstic acid is precipitated without the sulphurous acid causing any change in its aspect, even with heat.

Molybdate of ammonia acts otherwise; sulphurous acid causes it to become of a very fine blue in a very short time, but no precipitate is formed in the liquor, and it may be boiled in a close vessel without becoming turbid or discolored.

To dissolve the hydrate or carbonate of chrome in sulphurous acid, it must be suspended in a large quantity of water, and the liquor must be supersaturated with acid: this liquor is green. It is decomposed by boiling, and deposits the chrome which it contained in the state of granular and green subsulphite; ammonia does not render it turbid, any more than the alkaline carbonates; but these reagents communicate to it a faint wine color, similar to that of acetate of chrome. The alkaline sulphites do not precipitate the salts of chrome, even by aid of prolonged boiling.

When sulphurous acid gas is passed into a solution of neutral chromate of potassa, there is formed in it a considerable brown deposit of deutoxide of chrome; then the deposit turns green, and gradually redissolves, and we have finally a green liquor which contains sulphuric acid, hyposulphuric acid and sulphurous acid. On boiling this liquor, all the sulphurous acid is disengaged, and the chrome is almost entirely precipitated in the state of subsulphite of protoxide. Sulphurous acid immediately colors green the solutions of alkaline bichromate without rendering them turbid, and changes them into a mixture of sulphate and hyposulphate of chrome: no precipitate is formed by boiling.

The carbonate of cerium, as obtained by means of cerite, dissolves without difficulty in sulphurous acid. The salts of cerium are not rendered turbid, without heat, by the alkaline sulphites, but, by aid of ebullition, these salts are completely decomposed, as well as the pure sulphite, and all the metal is separated from it in the state of granular, white subsulphite, quite like yttria. If, besides cerium, there really exist in cerite two

other metals-lantanium and dydinium, it follows that all these three metals act in the same manner with sulphurous acid.

It is known that, in dissolving in nitric acid, all the oxides of manganese superior to the protoxide give a mixture of sulphate, hyposulphate and sulphite. In order to obtain the sulphate pure, the carbonate must be employed: the latter is completely dissolved in an excess of sulphurous acid; but if this excess be driven off by heat, a subsalt is precipitated which is sparingly soluble in water, but which easily redissolves in sulphurous acid. The solutions of manganese are not rendered turbid, cold, by sulphite of potassa; but, at the boiling temperature, they act with this reagent like pure sulphite. On the contrary, when sulphite of ammonia is added to those solutions, they are not rendered turbid, however long they may be boiled.

Iron, in the state of humid hydrate of peroxide, immediately dissolves in sulphurous acid: the native hydrate itself is appreciably soluble in it. The liquor, at first red, is afterwards almost entirely decolored. When an alkaline sulphite is poured into the solution of a salt of peroxide of iron, the liquor also immediately becomes of an intense red, even when it is very dilute; but it is almost instantaneously decolored when heated, and this decoloration is effected even without heat, spontaneously, in a very short time; sulphuric acid is formed, and the iron is reduced to the state of protoxide. The solutions are not rendered turbid by boiling, when the contact of the air is avoided; but if, after the excess of acid has been expelled, they be left exposed to the atmospheric action, there very speedily separates, especially with heat, a substance of a brown-red which must be a subsalt of peroxide of iron, and the liquor itself becomes perceptibly red.

The solutions of sulphite of iron are only partially precipitated by ammonia, and it appears even that they are not at all precipitated when they are sufficiently acid; but after the addition of ammonia, the iron is completely precipitated by the hydrosulphates, which would not have been the case with the pure sulphite, because a soluble hyposulphite would be formed.

The moist phosphate of peroxide of iron dissolves by the aid of heat in sulphurous acid and sulphite of ammonia, but slowly and with difficulty. If sulphite of ammonia be added to a solution of phosphate of iron, a great part of the latter is at first precipitated, but it is gradually redissolved by boiling. However, it is better to bring it first to the state of phosphate of protoxide by the addition of a sufficient quantity of sulphurous acid to the liquor; after that the latter