This induced me to combine strontian and oxalic acid in the following manner: 100 grains of a solution containing seven grains of real oxalic acid were neutralized by ammonia, and the oxalic acid precipitated by means of muriate of strontian. The salt obtained weighed 12.3 grains; of course it was composed of

Thus it appears that there are two oxalates of strontian, the first obtained by saturating oxalic acid with strontian water, the second by mixing together oxalate of ammonia and muriate of strontian. It is remarkable that the first contains just double the proportion of basę

contained in the second.

III. Decomposition of the Oxalates.

1. When oxalic acid, in the state of crystals, is exposed to heat, it is only partially acted upon, a considerable portion escaping without alteration; but when an alkaline or earthy oxalaté is heated, the acid remains fixed till it undergoes complete decomposition. The new substances into which the acid is converted, as far as my experience goes, are always the same, what oxalate soever we employ. They are five in number; namely, water, carbonic acid, carbonic oxyd, carbureted hydrogen, and charcoal.

2. The water is never quite pure. Though no sensible portion of oil can be perceived in it, yet it has always the peculiar smell of the water obtained during the distillation of wood; a smell which is usually ascribed

to

to oil. It commonly shews traces of the presence of ammonia, changing vegetable blues to green,' and smoking when brought near muriatic acid; but this minute portion of ammonia is probably only accidentally present. All the oxalates which I decomposed by distillation, were obtained by double decomposition from oxalate of ammonia; and though they are washed with sufficient care, yet I think it not unlikely that a minute portion of oxalate of ammonia might continue to adhere. Practical chemists know the extreme difficulty of removing every trace of a salt with which another has been mixed.

The carbonic acid remains partly combined with the base, which always becomes a carbonate, and partly makes it escape in the form of gas.

The carbonic oxyd and carbureted hydrogen make their escape in the form of gas: the charcoal remains in the retort mixed with the base, to which it communicates a grey colour: the quantity of it depends in some measure upon the heat. If the oxalate was exposed to a very violent heat, no charcoal at all remains. Hence it probably acts upon the carbonic acid united to the base, converting it into carbonic oxyd, as happens when a mixture of a carbonate and charcoal are heated.

3. I was induced to examine this decomposition with considerable attention, because I conceived that it would furnish the means of estimating the composition of ox-. alic acid; and I pitched upon oxalate of lime, as the salt best adapted for the purpose I had in view. A de. terminate quantity of this salt was put into a small retort, and gradually heated to redness. This retort was connected with a pneumatic trough by means of a long

glass

glass tube, having a valve at its extremity which allowed gas to issue out, but prevented any water from entering the tube. The experiment was repeated three

times.

4. A hundred grains of oxalate of lime, when thus heated, yield above sixty cubic inches of a gas, which is always a mixture of carbonic acid and inflammable air, nearly in the proportion of one part of the former to three and a half of the latter, reckoning by bulk. The specific gravity of the inflammable gas was 0.908, common air being 1.000; it burns with a blue flame, and when mixed with oxygen may be kindled by the electric spark. The loudness of the report depends upon the proportion of oxygen.

The smallest quantity of oxygen, with which it can be mixed, so as to burn by the electric spark, is 1-9th; the combustion is very feeble, and is atten led with no perceptible report. If the residue be washed in limewater and mixed with 1-9th of its bulk of oxygen, it be kindled a second time: this may be repeated five times, after which the residue cannot be made to burn.

may

The combustion becomes more violent, and the report louder, as we increase the proportion of oxygen, and both are greatest when the oxygen is double the bulk of the gas. As we increase the dose of oxygen, the combustion becomes more and more feeble; and five parts of oxygen and one of gas is the limit of combustion on this side for a mixture of six parts of oxygen and one of the inflammable air will not burn.

In these experiments the results differ materially from each other when the proportion of oxygen used is small

and

and when it is great. I am not able at present to account for this difference, which holds not only with respect to this gas, but every compound inflammable gas

which I have examined. This difference makes it impossible to use both extremes of the series: I make choice of that in which the proportion of oxygen is considerable, as upon the whole more satisfactory. The best proportion is one part of the gas and two parts of oxygen. The oxygen ought not to be pure, but diluted with at least the third of its bulk of azote, unless the gas be much contaminated with common air,

I have elsewhere detailed the method which I follow in analysing gases of this nature. The following table exhibits the mean of a considerable number of trials of

that is to say, 100 cubic inches of the gas when burnt combine with 91 cubic inches of oxygen; there are produced 93 inches of carbonic acid; and after the combustion these 93 inches alone remain, the rest being condensed. Hence we conclude that the other substance produced was water.

This result corresponds almost exactly with what would have been obtained if we had made the same experiment upon a mixture of 70 measures of carbonic oxyd and 30 measures of carbureted hydrogen, as will appear from the following table.

* See Nicholson's Journal, 16, 247.

Carbonic

Measures of

Measures of Measures of Diminution inflammable Gas Oxygen con- carbonic Acid

of

consumed.

sumed.

formed.

Bulk.

This coincidence is so exact, that I do not hesitate to conclude that the inflammable gas, which was the subject of experiment, was in reality a mixture of 70 parts of carbonic oxyd, and 30 of carbureted hydrogen. The specific gravity, indeed, which was 0.908, does not exactly agree with the specific gravity of such a mixture; for 2 measures of carbonic oxyd, and one measure of carbureted hydrogen, ought to form a mixture of the specific gravity 0.849, provided the specific gravity of carbonic oxyd be 0.956, and that of carbureted hydrogen 0.600; but this objection cannot be admitted to be of much weight, till the specific gravity of pure carbureted hydrogen be ascertained with more accuracy than has hitherto been done.

The results contained in the preceding table enable us to determine the composition of this inflammable air with considerable precision; for 100 cubic inches of it require 91 inches of oxygen, and form 93 cubic inches of carbonic acid. But it is known that carbonic acid gas requires for its formation a quantity of oxygen gas equal to its own bulk; therefore, to form 93 inches of it, 93 inches of oxygen gas must have been employed; but only 91 were mixed with the gas: therefore the gas itself must have furnished a quantity of oxygen, equivalent