200 
Mr. Gregor on a native Arseniate of Lead . 
into it, as long as it separated any precipitate. The clear fluid 
was poured off, and evaporated nearly to dryness, and a small 
quantity of white matter, thus obtained, was added to the 
former precipitate, which dried, and exposed to a low red 
heat weighed, whilst still warm, 40,8, which, according to the 
proportion of 33:100, established by Mr. Chenevix, implies 
13,4 1 6 of arsenic acid. 
5. The superfluous lead was now separated from the fluid 
by sulphat of soda, and filtered off. Ammonia precipitated a 
minute portion of flaky matter ; it weighed, after ignition, 0.2 
of a grain ; it consisted of silica and oxide of lead, and must 
be attributed to the nitrat 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 sulphat 
of soda. The clear decanted fluid was evaporated to a small 
volume, and sulphat of soda produced a further separation of 
white matter ; It was sulphat of lead, which after exposure to 
a low red heat, and weighed, whilst warm, = 47.5, which, 
upon the supposition that one hundred parts of sulphat of lead 
contain 6g. 74 of lead + 3-4$ of oxygen, is equivalent to 
34.77 of oxide of lead. 
2. The fluid, now freed from lead, deposited, on the affu- 
tion of an arseniat of lead is produced; but crystalline grains are, after a time, 
gradually deposited at the bottom of the vessel. But liquid nitrat of lead causes an 
immediate and abundant precipitate from these same dilute solutions. These tw© 
combinations therefore must he different. 
