178 On definite Proportions. 
MorRIATE OF THE PROTOKIDE OF LEAD. 
Some muriate of the protoxide of lead, which had been 
several times dissolved and crystallized, was thoroughly 
dried, and 40 grammes of it were ignited and melted in a 
small glass dish. A little of the salt evaporated, but the 
whole had only Jost -05 in weight. This salt appears, there- 
fore, to contain no water chemically combined with it, and 
the reason that it decrepitates on the first application of 
heat can only be the presence of moisture, which is me- 
chanically inclosed in the larger crystals, Indeed all the 
water which is the cause of the decrepitation of salts must 
be in this state; for when we take small crystals, for ine 
stance, of sulphate of potass or of common salt, they com- 
pletely retain their form and transparency; and if that 
which escapes were water of crystallization, it would na- 
turally be first separated at the surface of the crystals, and 
that which comes from the interior parts would find room 
to pass through the pores left in the superficial ones. 
a, Ten grammes of very finely powdered muriate of the 
protoxide of lead, which had been fused, were dissolved in 
nitric acid, and the nitrate of the protoxide of silver was 
added in order to obtain a precipitate. The clear liquor 
was evaporated to dryness in a glass dish, with the assistance 
of a gentle heat, and the dry mass was again dissolved in 
water. Hence I obtained a little more muniate ofthe prot- 
oxide of silver, which had been retained by the uncom- 
bined acid. ‘The muriate of silver, washed and dried, 
weizhed 10°32 gr., corresponding to 1:9644 of muriatic 
acid, ; 
b. Ten other grammes of the same muriate of the prot- 
oxide of lead were dissolved in nitric acid, and sulphuric 
acid was added in greater quantity than was necessary for 
the precipitation of the lead; the solution was then care= 
fully evaporated. As it cooled, notwithstanding the ex- 
cess of sulphuric acid, some crystals of the muniate were 
deposited. The saline mass, when perfectly dried, and 
heated so as to expel a part of the superflucus sulphuric 
acid, was well washed, and the sulphate of the. protoxide 
of lead being placed on a filter, some more water was 
poured on it. From this fluid a little more sulphate was 
separated by means of caustic ammonia.. The whole sul- 
phate collected, and well ignited, weighed 10°92 gr. and 
these contained, according to the preceding determination, 
80387 of the protoxide. Consequently the muriate of the 
protoxide 
