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which possessed the following properties. Its external appearance was similar to that of gum-arabic; but it was more easily reduced to powder, and had a peculiar bitter, biting, and sharp metallic taste. This easily soluble tungstate of ammonia, being exposed for an hour to a gentle red heat in a glass with a narrow mouth, fest 40 gr. of a light blue oxide, which at the commencement was yellow. These 40 gr. were put into a crucible, and exposed for an hour to a strong white heat in a blast furnace without any mixture of charcoal powder. It was converted into an oxide of a deep blue colour. Being mixed with charcoal powder, and treated as in experiment 16, a regulus was obtained in small grains, possessing the properties already described.

The salt remaining undissolved by the ammonia exhibited the properties of the quadruple compound, only it was somewhat more difficultly soluble, and probably contained a greater proportion of oxygen. It consisted of small clear crystals, and weighed 85 gr.

Exper. 20.-20 gr. of the quadruple compound were put into a glass vessel, and exposed to a heat raised by degrees till the glass melted. The resulting substance possessed the properties described in experiments 17 and 18, excepting that it was less blue, and more inclined to grey.

These last experiments show us not only that the preparation of pure tungstate of ammonia, by employing yellow oxide obtained from the triple compound of oxide of tungsten, potash, and muriatic acid, is very unprofitable; but that in this case a hitherto unknown quadruple compound of potash, oxide of tungsten, ammonia, and muriatic acid, is formed: and, lastly, they establish the conjecture hazarded in experiments 17 and 18, respecting the reality of the unfitness for reduction of the tungstate of ammonia altered as described in these experiments. This unfitness is the consequence of a mixture of the tungstate of ammonia with the so often mentioned triple compound, which has been dissolved by means of the ammonia, and converted into the quadruple compound.

Results established by the Experiments related in this Memoir.

1. The statement of other chemists, and particularly of Richter, respecting the great difficulty, or even impossibility, of obtaining a pure yellow oxide of tungsten by treating Scheele's tungstic acid with nitric acid, is established.

2. The employment of an oxide of tungsten obtained by the method described above is improper on two accounts. If we employ it after it has been exposed to a red heat, we obtain by means of it an apparently pure tungstate of ammonia; but for the extraction of the oxide of tungsten which it contains, an excessive quantity of ammonia is necessary; as by the red heat the oxide of tungsten is united with the undecomposed triple compound mixed with it, and forms a very cohesive compound, and therefore very difficultly acted on by ammonia. If we employ the oxide without exposing it to a red heat, we form, when we dissolve it in ammonia, a great quantity

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of a quadruple compound (the properties of which are given in experiment 10) consisting of oxide of tungsten, potash, ammonia, and muriatic acid; and only a very small quantity of tungstate of ammonia can be obtained. This shows us the necessity of employing pure oxide of tungsten in the formation of tungstate of ammonia.

3. Besides the yellow and dark blue oxides of tungsten, there seems to exist another of a dark brownish red or reddish brown colour. It may be obtained by the application of heat to the tungstate of ammonia, in consequence of the deoxidizing property of the ammonia. In respect to the degree of oxidation, it seems to lie between the yellow and the blue oxides.

4. The complete reduction of oxide of tungsten by the method above described is a much easier process than the fusion of the reduced metal. This holds likewise with molybdenum, manganese, and other difficultly fused metals.

5. It is exceedingly probable that the failure which different chemists have experienced in their attempts to reduce the oxide of tungsten, was owing to a mixture of the triple compound with the oxide employed by them.

6. The statement of the Elhuyarts and of Allen and Aikin respecting the specific gravity of this metal is confirmed. We may consider 17.4, the mean of preceding statements, as near the truth. The other statements respecting the colour, lustre, hardness, and brittleness, of our metal, are likewise confirmed.

7. The presence of a portion of Scheele's tungstic acid in the oxide of tungsten prevents its complete reduction, and causes it to run into a slag.

ARTICLE VII.

Description of an Elementary Galvanic Battery. By W. Hyde Wollaston, M.D. Sec. R. S.

DEAR SIR,

(To Dr. Thomson.)

AGREEABLY to your request, I now send you a description of a small battery which I showed you some time since, and shall feel obliged by the insertion of it in your Annals.

Since the ignition of metallic wires is highly instructive with respect to the vast quantity of electricity evolved during the solution of metals, I made, about three years since, a series of experiments for the purpose of ascertaining the most compendious form of apparatus by which visible ignition might be shown.

The result of these trials was, that a single plate of zinc one inch square, when rightly mounted, is more than sufficient to ignite a VOL. VI. N° III.

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wire of platina * of an inch in diameter, even when the acid employed is very dilute. But for this purpose each surface of the zinc must have its counterpart of copper or other metal opposed to it; for when copper is opposed only to one face, the action on the posterior surface of the zinc is wasted to little or no purpose.

The smallest battery that I formed of this construction consisted of a thimble without its top, flattened till its opposite sides were about of an inch asunder. The bottom part was then nearly one inch wide, and the top about; and as its length did not exceed of an inch, the plate of zinc to be inserted was less than & of a square inch in dimensions.

Previously to insertion, a little apparatus of wires, through which the communication was to be made, was soldered to the zinc plate, and its edges were then coated with sealing-wax, which not only prevented metallic contact at those parts, but also served to fix the zinc in its place by heating the thimble so as to melt the wax.

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A piece of strong wire, bended so that its two extremities could be soldered to the upper corners of the flattened thimble, served both as a handle to the battery, and as a medium to which the wires of communication from the zinc could be soldered.

The conducting apparatus consisted in the first place of two wires of platina about of an inch in diameter and one inch long, cemented together by glass in two parts, so that one end of each wire was united to the middle of the other. These wires were then tinned, not only at their extremities for the purpose of being soldered to the zinc and to the handle, but also in the middle of the two adjacent parts for receiving the fine wire of communication.

One inch of silver wire of an inch in diameter, containing platina at its centre part of the silver in diameter, was then bended so that the middle of the platina could be freed of its coating of silver by immersion in dilute nitrous acid. The portion of silver remaining on each extremity served to stretch the fine filament of platina across the conductors during the operation of soldering. A little sal-ammoniac being then placed on the points of contact, the soldering was effected without difficulty, and the two loose ends were readily removed by the silver attached to them.

It should here be observed, that the two parallel conductors cannot be too near each other provided they do not touch, and that on this account it is expedient to pass a thin file between them (pre-* viously to soldering on the wire) in order to remove the tin from the adjacent surfaces. The fine wire may thus be made as short as from to of an inch in length; but it is impossible to measure with

* For the method of drawing fine wires of platina, by coating them with a quantity of silver, I must refer to the description which I have formerly given of that contrivance. Phil. Trans. 1813, p. 114. See Annals of Philosophy, vol. ii. p. 233.

precision, since it cannot be known at what points the soldering is in perfect contact.

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The acid which I have employed with this battery consists of one measure of sulphuric acid diluted with about 50 equal measures of water; for though the ignition effected by this acid be not permanent, its duration for several seconds is sufficient for exhibiting the phenomenon, and for showing that it does not depend upon mere contact, by which only an instantaneous spark should be expected. Although in this description I have mentioned a wire of an inch in diameter, I am doubtful whether this thickness is the best. I am, however, persuaded that nothing is gained by using a finer wire; for though the quantity of matter to be heated is thus lessened, the surface by which it is cooled does not diminish in the same ratio; so that where the cooling power of the surrounding atmosphere is the principal obstacle to ignition, a thicker wire, which conveys more electricity in proportion to its cooling surface, will be more heated than a thin one, a fact which I not only ascertained by trials on these minute wires, but afterwards took occasion to confirm on the largest scale by means of the magnificent battery of Mr. Children in the summer of 1813.

I remain, dear Sir, ever very faithfully yours,

Buckingham-street, Fitzroy-square,»
Aug. 5, 1815.

WM. H. WOLLASTON.

ARTICLE VIII.

Objections to Sir H. Davy's Theory of Chlorine. By J. Berzelius, M.D. F.R.S. Professor of Chemistry at Stockholm.

SIR,

(To Dr. Thomson.)

Stockholm, June 6, 1815. I HAVE just received the English scientific journals for the last seven months. In one of the numbers of your Annals you express. a wish that I should explain how the theory of Sir H. Davy respecting the nature of muriatic acid is inconsistent with the law respecting the combination of oxides with each other. I therefore give the following statement.

According to the old theory, muriate of lead is composed of 100 parts acid and 410 of oxide of lead. The submuriate of lead is composed of 100 acid + 410 x 4 = 1640 oxide. This salt, when prepared by precipitation, contains combined water, which may be. separated by heating the salt in a retort. The quantity of this water amounts to 133 parts for every 1740 parts of the dry salt. Now the oxygen in this water is just equal to that in the oxide of lead present. You know, likewise, that in the submuriate of copper

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100 parts of the acid are combined with 589 parts of oxide of copper and with 1334 of water. Here the oxygen in the water is likewise equal to that in the oxide.

You are aware, I presume, that neither Davy, nor the partisans of the new theory, agree with themselves in what ought to be considered as a hydro-chlorate or a chloride. Sometimes they speak of chloride of potassium, barium, copper, iron; sometimes they give the name of muriate or hydro-chlorate to these bodies. Such is the looseness of the theory, that we cannot point out any essential difference between the hydro-chlorates and chlorides. (Yet if we confine ourselves to analogy, to which these chemists, however, do not seem to attach any value, there is a decided difference between the sulphuret of potassium and the hydro-sulphuret of potash, one, of which represents the chloride, and the other the hydro-chlorate.) Therefore when we wish to discuss their opinions, we must foresee all their methods of escaping from the examination; because if you prove that such a body cannot be a chloride, they answer that it is a hydro-chlorate, decomposing and forming water at the pleasure of the hypothesis, with a facility which has no other example in the whole science of chemistry; for the sulphurets, phosphurets, and tellurets, of the alkaline metals decompose likewise water; but water in these cases cannot be formed at pleasure, provided the access of air be withheld. If we ask the partisans of the new theory what is their opinion of the composition of the submuriates in question, they will immediately answer that they are real subhydrochlorates, composed of hydro-chloric acid, oxide of copper, and water. But if the existence of such a hydro-chloric acid be real, it is to be supposed that the subhydro-chlorates in question are composed according to the same laws as all the other salts.

We must then, in order to convert the 100 parts of muriatic acid (supposed by the old theory) into hydro-chloric acid, take away the fourth part of the 133 of water, the oxygen of which constitutes an integrant part of the chlorine, and the hydrogen of which added to the chlorine produces hydro-chloric acid. The weight of the metallic oxide remains the same. The 133-5 parts of water, then, which the analysis gives, do not exist wholly in the salt in the state of water. Only 100 2 parts exist in that state. The remaining 33.3 parts are produced by the operation when the hydrogen of the acid unites to a portion of the oxygen of the oxide in order to produce a chloride. But the oxygen of the metallic oxide is 117-8, while that of 100 2 parts of water only amounts to 88.6; that is to say, precisely three-fourths as much as the oxygen of the base. Here, then, we have a body composed of an acid without oxygen, of an oxide base, and of water of combination. The oxygen of the water ought to be in this case, as in all other salts, both neutral and with excess of base, a multiple or a submultiple by a whole number of that of the base. But we have just seen that it amounts only to three-fourths of it. Hence it follows that either the hypothesis of Davy, or the rule concerning the combination of oxides, is inaccu

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