Chemistry. xl 
black colour, and is completely converted into protoxide. The 
nitric acid contains in solution a portion of protoxide. When 
kept for some time, it lets fall an insoluble subnitrate, which is 
gradually changed into peroxide of tin. Besides the protoxide, 
there is a yellowish light matter which floats about in the liquid, 
and which may be separated by the filter. It is a protohydrate 
of tin. Acetic acid, when left in contact with tin filings, 
dissolves a portion, and converts it into protacetate of tin, but 
the residual tin filmgs are not oxidized.*—(See Giornale di 
- Fisica, Chimica, &c. 1818, p. 378.) The observations which 
M. Cassola makes on the peroxide of tin contain nothing 
which has not been long known to chemists. This peroxide is 
not white, as is stated in some recent systems of cheiuastry, but 
yellow ; and it is insoluble in all the acids which | have tried. 
Its hydrates (fur there are several) are of a fine white colour, 
and dissolve readily in muniatic, but not in nitric acid. 
13. Mercury.—M. de Biaimville has made an observation 
which seems entitled to attention, and which, therefore, [ notice 
here. It is weil known to-chemists that mercury amalgamates 
very easily with gold, silver, lead, tin, zinc, bismuth, and arsenic; 
but it does not amalgamate with iron, cobalt, and nickel; or at 
least the amalgams of these metals cannot be formed without 
considerable difficulty. Now the observation of M. de Blainville 
is, that when these metals are united to arsenic, the alloy amal- 
gamates very readily; so that by the intervention of this metal, 
we can easily procure amalgams of those metals which do not, in 
other circumstances, unite to mercury.—(Jour. de Phys. lxxxiv. 
267.) 
I was rather surprised to find (Annals of Philosophy, xii. 67) 
that Mr. Donovan had concluded from his experiments that the 
‘ composition of the oxides of mercury is as follows : 
Protoxide..... 100 mercury + 4°12 oxygen 
Peroxide. .... 100 mercury + 7°82 oxygen 
These numbers are inconsistent with the doctrine of definite 
proportions, which has been perfectly well established. The 
experiments of Fourcroy, Sefstrom, &c. have shown that the 
composition of these oxides is as follows : 
Protoxide. ...... 100 mercury + 4 oxygen 
Peroxide........ 100 mercury + 8 oxygen 
14. Copper.—It seems hardly worth while to recall the attention 
* I may observe here that I had the curiosity to try this process, but did not 
find it to answer. The mode which I have usually followed to obtain protoxide 
of tin is to dissolve that metal by means of heat in muriatic acid. I put the solution 
in‘o a well-stopped phial, placing in it a number of slips of tin. These slips 
graduaily reduce the whole of the dissolved ivetal to the state of protoxide. I 
tiave sometimes seen the dissolved tin precipitated upon the tin in crystalline plates, 
having the metallic lustre. P 
