58 
“ Some endeavours to ascertain the nature of the insoluble 
form of Soda existing in the residue left on Causticizing 
Sodium Carbonate Solutions with Lime” (Part II.), by Wat- 
son Smith, F.C.S., Assistant Lecturer on Chemistry in the 
Owens College, and Mr. W. T. Liddle. Communicated by 
Professor C. Schorlemmer, F.RS. 
At the close of our last paper we mentioned that it was 
our intention to try certain further experiments with the 
crystalline precipitate obtained by mixing solutions of 
sodium carbonate and lime water and warming, and also 
with ordinary “ lime-mud ” from the causticizing pan of an 
alkali- works, after the usual washing and draining. The 
experiments we proposed to try were : 
(1) The effect of ignition upon the crystalline precipitate 
prepared as above, and upon the “lime-mud” of 
the soda- works. 
(2) The effect of long continued boiling with water. 
(3) The effect of boiling with some saline solution, as for 
example with sodium sulphide. 
Two fresh samples of the crystalline precipitate were 
now prepared, each in rather a different manner from the 
other. In the first case lime water was used in slight 
excess, and the sodium carbonate solution was dilute ; in the 
second a strong solution of sodium carbonate was employed, 
the sodium carbonate being in excess. The precipitates 
obtained in both cases appeared under the microscope simi- 
larly crystalline; we will call them A and B respectively. 
On analysis the following results were obtained, after the 
precipitates had been washed with hot water till quite free 
from all soluble alkali : 
A. B. 
Calcium carbonate ...98*07%.: 98*11 
Sodium carbonate ... 1*93% 1*88 
100*00 99*99 
(1) A weighed quantity of dried precipitate, previously 
well washed from all soluble alkalinity, was now ignited 
