364: NATIVE ARSENIATE Or LEA»«, 



Analysis^ exposed to a low red licat, weighed, while still warm, 40*8, 



which, according to the proportion of 33 : 100, established! 

 by Mr. Cheiicvix, implies, 13-46 of arsenic acid. 



5. The superfluous lead was now separated from the fluidl 

 by sulphate of soda, and filtered off. Ammonia precipi- 

 tated a minnte portion of flaky matter; it weighed, afteF 

 ignition, 02 of a grain ; it consisted of silica and oxide of 

 lead, and must be attributed to the nitrate of lead employed. 

 B. 1. The yellowish white residuum (a) ( A, 2.) was dis- 

 solved without effervescence in nitric acid, except a minute 

 portion of silica, which, after ignition, =0-28. A white 

 heavy matter was thrown down from this solution, by liquid 

 sulphate of soda. The clear decanted fluid was evaporated 

 to a small volume, and sulphate of soda produced a farther 

 separation of white matter. It was sulphate of lead, which, 

 after exposure to a low red heat, and weighed, while warm, 

 = 47*5; which, upon the supposition that one hundred 

 parts of sulphate of lead contain 69-74 of lead +3*48 of 

 pxigen, are equivalent to 34*77 of oxide of lead. 



2, The fluid, now freed from lead, deposited? on the 

 affusion of ammonia, a greenish matter, which, after ig- 

 nition, became red, and = 0-033 of a grain. It was oxide 

 of iron. 



C. 1. One hundred grains of larger crystals, some of. 

 which were hollow, and the surfaces of which were slightly 

 and partially covered with silky fdaments, treated in the 

 same way, yielded 93-283 of sulphate of lead, equivalent to 

 69-76 of oxide ; and 80 of arseniate of lead, whieh indicate 

 26-40 of arsenic acid. The oxide of iron, in this case, 

 amounted to only 0-05 of a grain, and the residuary silica 

 was in too small a quantity to be weighed. 



2. I have endeavoured to decompose this fossil by boiling 

 it to dryness in a solution of four times its weight of the 

 purest subcarbonate of potash, and exposing the dry mass, 

 for a very short time, to a low red heat; but I found, that 

 only a part of the arsenic acid had united to the alkali; th^ 

 larger portion of it was detected in the nitric solution of 

 the fesiduum; but the relative proportions of the oxide and 

 the acid were found to correspond almost ex3,ctly with the 

 foregoing statement of them. 



3. I 



