44 
BRITISH ASSOCIATION.— 1835 . 
On two occasions a lead salt was obtained in plates like the 
baryta salt, and apparently containing two atoms of water ; but Pro¬ 
fessor Kane has not determined the exact circumstances necessary 
to the production of this form, and consequently its examination yet 
remains to be made. 
The salts of copper, nickel, soda, ammonia, lime, magnesia, alu¬ 
mina, and iron have been formed by double decomposition, but their 
properties would occupy too much space in describing. The mode 
of obtaining them indicates their composition. 
All those salts that contain crystallization w 7 ater, lose it (efflo¬ 
rescing) when dried over sulphuric acid. This method was em¬ 
ployed to determine the quantity of such water present. 
Dr. Dalton observed that he had analysed pyroxylic spirit some 
years since (in 1829), and found it to be composed of an atom of 
olefiant gas united chemically to one of water. This was inferred 
from burning its vapours with oxygen in Volta’s eudiometer. He 
also ascertained that burning it in a lamp produced the same heat 
as burning alcohol diluted so that the two liquids contained the same 
relative quantities of olefiant gas and w T ater. At the same time he 
found pyroacetic spirit to be constituted of 3 atoms of carbon, 2 of 
hydrogen, and 1 of oxygen, or rather 1 atom carbonic oxide holding 
2 of olefiant gas: this was discovered by burning the vapour with 
oxygen in Volta’s eudiometer. 
On some Combinations of Protochloride of Platina with Protochloride 
of Tin. By Robert J. Kane, M.D., M.R.I.A. 
These bodies unite in two different proportions; that containing 
least tin is of an olive brown colour, crystalline, and very deliques¬ 
cent ; decomposed by much water, giving muriatic acid and mixed 
oxides of tin and platina. The second, which contains most tin, is 
of an intensely red colour, soluble in a small quantity of water, giv¬ 
ing a splendid red solution, but is decomposed by much water, giving 
muriatic acid, and a chocolate powder which contains the proto¬ 
chlorides of platina and tin and protoxide of tin. By acting on this 
powder by ammonia, a black matter in crystalline grains is obtained, 
which -when heated burns like tinder, with formation of peroxide of 
tin, and platina is reduced. 
The colour of the solution was found by Professor Kane, on ex¬ 
amination by a prism, to be an absolutely homogeneous red. 
Professor Johnston read a paper on the physical cause of certain 
optical properties observed in chabasie. 
The nature and amount of the double refraction are found to vary 
according to the course taken by the ray; and this Mr. Johnston 
conceives to arise from the fact of the index for quartz being nega- 
