308 Dr Turner on the Composition of the Minerals 



arseniate of lead, was removed by sulphuretted hydrogen ; 

 and the lime, after neutralizing exactly, was separated by 

 oxalate of ammonia. The oxalate of lime was exposed to a 

 white heat, and 1.885 grains, or 29.466 per cent, of pure 

 lime, were thus procured. 



The crystallized mineral is accordingly composed of 



5.928 94.725 



There has been considerable loss in this analysis, and there- 

 fore it cannot be relied on for showing the actual composition 

 of the mineral itself. It will be obvious, however, in com- 

 paring the results of this and the next analysis together, that 

 the arsenic acid and lime are in both minerals united in the 

 same proportion. 



Analysis of the Second Species. 

 The analysis was conducted as the preceding. In one ex- 

 periment, 2.495 grains lost from ignition 0.405 grains, or 

 13.965 per cent, of water. In another, 0.995 gr. lost 

 0.145 grains, or 14.673 per cent. The mean is 14.319. 



From 3.29 grains of the anhydrous mineral, I obtained 

 6.26 grains of ignited arseniate of lead ; equivalent to 2.23 

 grains, or 67-781 per cent, of arsenic acid. 



The lime weighed 1.09 grains, which is 34.343 per cent. 

 The crystallized mineral is hence composed of 

 Arseniate of Lime - 85.681 



Water - - - 14.319 



100.000 



And the anhydrous of 



Arsenic acid - 2.23 67.78 



Lime - - - 1-09 33.13 



3.32 100.91 



The data upon which these calculations were founded are 

 those of Dr Thomson. Arseniate of lead is supposed to be a 



