40 
THE TANNINS. 
There are many sources of error in this process, as 
has been pointed out by Ran, who says, “A 5-per-cent, 
solution of gallotannic acid had a specific gravity of 
1.01841. The density of distilled water being 1.0000, 
the 5 per cent, gallotannic acid was represented by the 
increase in specific gravity 0.01841. A solution of cane- 
sugar was prepared having specific gravity 1.01646, 
and 5 per cent, of the same gallotannic acid dissolved 
therein. The specific gravity of the latter solution was 
then found to be 1.03398; consequently the same per¬ 
centage of tannin was in this case represented by a 
somewhat smaller increase in specific gravity, 0.01752.” 
The same author by experiments showed that the col¬ 
oring-matters of logwood and Persian berries were 
largely absorbed by the hide powder along with the 
tannin. 
Simand recommended the use of bone tissue instead 
of hide powder. This bone tissue he prepared by 
taking tubular bones free from joints, macerating them 
for two days with a five-per-cent, solution of soda, 
thoroughly washing with water, reducing to smaller 
pieces, and treating with dilute hydrochloric acid until 
softened, then washing and passing through a grind¬ 
ing machine while still wet. This comminuted mass 
was treated with dilute hydrochloric acid, thoroughly 
washed, pressed, and dried. 
Simand and Weiss estimated the tannin in extracts 
by hide powder, which they prepared from fresh skin 
by washing, unhairing, treating with dilute hydro¬ 
chloric acid, stretching, and drying. The skin was then 
planed fine, dried, and worked through a fine sieve. 
The watery residue from 5 grammes of this powder 
