27 
addition produces a thick yellow precipitate, which rapidly 
changes in contact with air and thereby becomes green. 
Acetate of Lead also produces a thick precipitate of white 
colour. These precipitates contain, besides the metallic 
oxide, Lime, Phosphoric and Sulphurous Acids. Chloride 
of Barium precipitates the solution directly, and Chloride 
of Magnesium after some standing. 
The solution of Phosphate of Lime in Sulphurous Acid 
possesses the taste and smell of the acid, but to a much 
smaller extent than an aqueous solution of the acid contain- 
ing the same amount of Sulphurous Acid. 
Under the influence of boiling heat the Phosphate solution 
is decomposed slowly, Sulphurous Acid escapes, and a heavy 
white crystalline precipitate is formed. Under the micro- 
scope it appears as composed of crystals of the hexagonal 
system, like those of rock-crystal. Washed and dried over 
Sulphuric Acid, it contained : 
Sulphurous Acid 15*61 
Sulphuric Acid 0 °2 3 
Lime 39*89 
Phosphoric Acid 34*48 
Water 9*08 
99*29 
These numbers agree with the formula 3CaO, P0 5 , S0 2 , 2HO, 
the calculated numbers of which are 
SQ 2 ... 32 ... 15*58 
3CaO ... 84 ... 40*89 
P0 5 ... 71*4 ... 34*76 
2HO ... 18 ... 8*77 
205*4 100*00 
This Sulphited Phosphate of Lime has no smell or taste, and 
is distinguished from all sulphites by its stability. Heated 
in an air bath for three hours to 130 C it lost 0*64 per cent of 
water, but the amount of Sulphurous Acid remained un- 
changed, neither had a humid atmosphere the slightest 
