07 
Ordinary Meeting, Janimry 2 qI:}i; 1876. 
E. W. ’Binney, F.R.S., F.G.S., Vice-President, in the Chair. 
'^Stannic Arsenate,” by William Caeleton Williams, 
F. C.S., Demonstrator in the Chemical Laboratory of the 
Owens College. 
A mixture of moderately concentrated aqueous solutions 
of stannic chloride amd arsenic acid gradually thickens on 
standing, and after the lapse of two or three weeks solidi- 
fies, forming a transparent colourless noncrystalline mass. 
In order to ascertain the composition of this substance I 
subjected a considerable quantity of it to dialysis; hydro- 
chloric acid and the excess of arsenic acid or stannic chloride 
passed througl) the dialyser, leaving a gelatinous residue of 
pure stannic arsenate. This jelly is heavier than water, it 
floats in a liquid having a specific gravity 1T85. Strong 
acids, and solutions of caustic potash or soda, dissolve it 
readily. In water it dissolves very slov/ly. From this 
aqueous solution certain reagents reprecipitate the arsenate 
of tin as a gelatinous mass, identical in its appearance, proper- 
ties, and composition vrith the original jelly. These reagents 
are hydrochloric, nitric, and sulphuric acids, the chlorides of 
barium, calcium, ammonium, and iron, also silver nitrate 
and pota^ssium iodide. Alcohol, acetic acid, sodium phos- 
phate, mercuric chloride, and the carbonates of sodium, 
potassium, amd ammonium, do not produce any change. 
This substance contains a large amount of water, the 
greater pa.rt of v/hich is expelled at a temperature of 100° C, 
A small quantity however is retained most pertinaciously, 
and is not driven off at 200°, Below a dull red heat decom- 
position takes place and fumes of amsenious oxide escape. 
51 ’9 grm. dried at 100° C, left 1'9 grin, residue. Loss of 
water = 50 grm. or 96*3 per cent. 
The residue somewhat resembles gum arable in appear- 
Proceedings — Lit. & Phil, Soc. — Vol. XV. — No. 6. — Session 1875-6. 
