129 
Ordinary Meeting, March 7th, 1871. 
E. W. Binney, F.R.S., F.G.S., President, in the Chair. 
“ The Action of Sulphurous Acid on Phosphates,” by Dr, 
B. Wilhelm Gerland, Macclesfield. — Communicated by 
R. Angus Smith, Ph.D., F.R.S. 
The researches which this paper describes, lead to the 
following conclusions : — 
1. An aqueous solution of sulphur dioxide acts upon seve- 
ral phosphates, not by decomposing them, like other strong 
acids, but by combining with them forming, soluble com- 
pounds. Basic phosphates require from 4 to 6, and neutral 
phosphates 2 mols. of sulphur dioxide for solution. These 
solutions part less readily with their sulphur dioxide than the 
simple aqueous solution of the latter, and those of the neutral 
phosphates more easily than those of the basic phosphates. 
From some of these solutions the original phosphate can be 
again obtained, from others a less basic salt, but the de- 
composition in the solutions of this class does not proceed 
to the formation of phosphoric acid. 
The following phosphates belonging to this class have 
been examined : 
a. Tricalcium phosphate is abundantly soluble in water 
and sulphur dioxide. The concentrated solutions undergo 
a slow decomposition at temperatures above 18° C., and 
form besides calcium sulphite, dicalcium- and mono- 
calcium- phosphate. Both concentrated and dilute solutions 
deposit mixtures of calcium sulphite and dicalcium hydric 
phosphate by addition of alcohol, by exposure in vacuum, 
or by boiling under reduced pressure. Boiling under at- 
PEdcmsDiNos — L it, & Phil. Soc.— Vol. X.— No. 12,— Session 1870-71. 
