observations in some measure rest upon the analysis of oxalate of lime, I thought it worth while to verify that analysis in the following manner.

100 grains of crystallised oxalic acid were dissolved in 1000 grains of water, making a solution which weighed 1100 grains.

It is obvious that every 100 grains of the above solution contained 9.09 grains of crystal of oxalic acid, equivalent, according to the preceding analysis, to seven grains of real acid.

100 grains of this solution were gradually mixed with lime-water till the liquid ceased to produce any change on vegetable blues. The oxalate of lime thus formed being well dried, weighed 11.2 grains. Exposed to a violent heat in a platinum crucible, this salt left 4.2 grains of pure lime. Hence it was composed of

7 acid, or per cent. 62.5 acid.

Thus we have obtained exactly the same result as in the former experiment, both as far as relates to the composition of oxalate of lime, and likewise to the proportion of water of crystallisation in crystallised oxalic acid.

The lime-water necessary to saturate the acid amounted to 3186 grains. Hence, it contained onlyth of its weight of lime.

3. The oxalates of barytes and strontian are white, tasteless powders, which may be obtained by mixing oxalate of ammonia with the muriates of these alkaline earths. It is said that these earths are capable of form

ing

ing soluble superoxalates with this acid; but I have not tried the experiment. These oxalates, as well as oxalate of lime, are partially soluble in the strong acids.

4. Oxalate of magnesia is a soft white powder, bearing a considerable resemblance to oxalate of lime. It is tasteless, and not sensibly soluble in water; yet when oxalate of ammonia is mixed with sulphate of magnesia, no precipitate falls; but if the solution be heated and concentrated sufficiently, or if it be evaporated to dryness, and redissolved in water, in both cases the oxalate of magnesia separates in the state of an insoluble powder.

5. Oxalate of potash readily crystallises in flat rhomboids, commonly terminated by dihedral summits. The lateral edges of the prism are usually bevelled. The taste of this salt is cooling and bitter. At the temperature of 60o it dissolves in thrice its weight of water. When dried on the sand-bath, and afterwards exposed in a damp place, it absorbs a little moisture from the atmosphere.

This salt combines with an excess of acid, and forms a superoxalate, long known by the name of salt of sorrel. It is very sparingly soluble in water, though more so than tartar. It occurs in commerce in beautiful four-sided prisms attached to each other. The acid contained in this salt is very nearly double half what is contained in oxalate of potash. Suppose 100 parts of potash; if the weight of acid necessary to convert this quantity into oxalate ber, then 2 r will convert it into superoxalate.

6. Oxalate of soda readily crystallises. Its taste is nearly the same as that of oxalate of potash. When heated, it falls to powder, and loses the whole of its water of crystallisation. Soda is said to be capable of combining

combining with an excess of acid, and of forming a superoxalate. I have not tried the experiment.

7. Oxalate of ammonia is the most important of all the oxalates, being very much employed by chemists to detect the presence of lime, and to separate it from solutions. It crystallises in long transparent prisms, rhomboidal, and terminated by dihedral summits. The lateral edges are often truncated, so as to make the prism 6 or 8-sided. Sometimes the original faces of the prism are nearly effaced.

The taste of this salt is bitter and unpleasant, somewhat like that of sal ammoniac. At the temperature of 60°, 1000 grains of water dissolve only 45 grains of this salt. Hence, 1000 grains of saturated solution of oxalate of ammonia contain only 43.2 grains of this salt. The specific gravity of this solution is 1.0186. As it may be useful to know the weight of this salt contained in solutions of different specific gravities, I have thought it worth while to construct the following table:

Weight of Oxalate Specific gra-Weight of Oxalate Specific graof Ammonia in 100 vity of the of Ammonia in 100 vity of the parts of the solu- solution parts of the solu- solution tion. 60°.

at

at

tion.

60°.

8. To determine the composition of these salts, I took seven different portions of a diluted oxalic acid solution, each weighing 100 grains, and containing seven VOL. XIII.-SECOND SERIES. Y y

grains

grains of real oxalic acid. To each of these portions I added respectively potash, soda, ammonia, barytes water, strontian water, and lime water, till it ceased to produce any change. The liquid was then evaporated to dryness, and the residue, after being well dried on the steam-bath, was weighed. Each of these salts contained seven grains of acid; the additional weight I ascribed to the base. Hence I had the following table, which exhibits the weight of each salt obtained, and its composition deduced from that weight.

The composition of these salts, reduced to 100 parts,

is given in the following table.

Oxalate Oxalate Oxalate Oxalate Oxalate Oxalate Oxalate of of of of of of of Ammonia. Magnesia. Soda. Lime. Potash. Strontian. Barytes.

Acid....74.45 73.68 63.63 62.50 44.87 39.77 41.16 Base....25.53 26.32 36.37 37.50 55.13 60.23 58.84

Total....100. 100. 100. 100. 100. 100. 100.

* The oxalate of magnesia was obtained by neutralizing the oxalic acid solution with ammonia, then mixing it with sulphate of magnesia, evaporating the solution to dryness, and washing the insoluble oxalate of maguesia with a sufficient quantity of water.

But

But, for practical purposes, it is more convenient to consider the acid as a constant quantity. The following table is constructed upon that plan.

9. In the preceding statement, no account has been taken of the water of crystallisation which might still remain attached to the salts, notwithstanding the heat to which they were exposed. There is reason to believe, however, that in most of them this water must be so small, that it may be overlooked without any great error. Oxalates of soda and of ammonia, I have reason to believe, lose all their water of crystallisation at a moderate heat. This is the case also with oxalates of lime and barytes, and I presume that the oxalates of strontian and magnesia are not exceptions; but oxalate of potash retains its water much more obstinately. believe that in that salt the weight of acid and of base are nearly equal, and that when dried in the temperature of 212o it still retains nearly 10 per cent. of water; but I have not been able to establish this opinion by direct experiment.

The composition of oxalate of strontian in the preceding table was so different from what I expected, that I repeated the experiment; but the result was the same. This

Yy 2