On the Influence of Boiling on Cassava. 
By Ernest E. H. Francis, F.C.S., F.I.C. 
N 1796, Dr. Clarke of Dominica on describing 
the fatal effects resulting to negroes from 
drinking bitter cassava juice, compared the 
action of the poison to prussic acid, and Dr. Fermin, by 
experiments made at Cayenne, proved that the poison 
like prussic acid, was volatile and could be isolated by 
distillation. Subsequently, M. M. Henry and Boutron- 
Charland by analysing bitter cassava juice imported into 
France, ascertained that the poison was prussic acid, 
and, in 1838, Dr. Christison confirmed their discovery 
by an examination of some well preserved juice from 
Demerara. 
Notwithstanding this early identification of the poison, 
no attempt had apparently been made to determine the quan- 
tity yielded by the plant, until in the year 1877, the pre- 
sent writer (then in Trinidad) undertook an inquiry into 
the subject. An examination was made not only of bitter 
cassava but also of a number of samples of sweet cassava, 
and contrary to expectation the latter were found to con- 
tain nearly as much prussic acid as the former. The 
results of the inquiry are published in two memoirs, 
the first in the London Analyst for April 1877, the 
second, a more extended one, in the Proceedings of the 
Scientific Association of Trinidad, for the same year. 
Fifteen samples of sweet cassava were obtained from 
the public markets and from different cultivators in 
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