Dr THOMAS THOMSON on some Experiments on Gold. 31 



I may mention another example of a muriate, which cannot, 

 without great violence, be viewed as a chloride, I mean the per- 

 muriate of tin- 



I have shown, in " The First Principles of Chemistry," that 

 the atomic weight of tin is 7'25, and that it forms two oxides, the 

 protoxide, which is black, and the peroxide, which is yellowish- 

 white. Protoxide of tin is composed of 1 atom tin + 1 atom oxy- 

 gen, and its atomic weight is 8'25 ; while peroxide of tin is a 

 compound of 1 atom tin -}- 2 atoms oxygen, and its atomic weight 

 is 9'25. Muriatic acid combines with each of these oxides, and 

 forms with each crystallisable salts. Both of these salts may be 

 formed by dissolving tin in muriatic acid. And I have got them 

 both in Mr MONTEATH'S Turkey-red work near Glasgow, where tin 

 is dissolved in muriatic acid in large quantities, to prepare the 

 usual mordant for dyeing. Permuriate of tin is the mordant 

 used ; but, occasionally, protomuriate of tin crystallizes likewise ; 

 and as it does not answer as a mordant, they were in the habit of 

 throwing it away, till I ascertained its nature. 



The protomuriate of tin is a white salt, which crystallizes in 

 large oblique four-sided prisms, having usually one of the acute 

 edges of the prism replaced by a tangent plane. It strongly red- 

 dens vegetable blues, probably because the crystals always shoot in 

 a solution containing a large excess of acid. Lustre rather silky ; 

 but the salt is transparent. The taste is acid, and very acrid and 

 disagreeable. Specific gravity 2'656. 



When put into water, the crystals dissolve, with the exception 

 of a few white flocks of hydrated tin. When heated, it melts, 

 and flows like nitrate of silver, quite transparent and colourless ; 

 then it becomes dry, and a white matter remains, which is soluble 

 in water. It dissolves in alcohol with the same opalescence as in 

 water. In oil of turpentine it does not dissolve, but becomes yel- 

 lowish and opaque, and increases in volume. Its constituents were 

 found to be 



