516 poisons : their effects and detection. [§ 676. 
The matters are finely divided and boiled with water feebly acidulated 
with hydrochloric acid. 
Care must be taken that, on boiling, the weak acid reaction is re¬ 
tained, and that this manipulation only lasts a few minutes. 
The insoluble portion is filtered off, and the 
filtrate evaporated, either in the gas-oven or on 
the water-bath, to syrupy consistency. If the 
substances are offensive, as alcoholic and watery 
extracts of flesh usually are, the use of Bocklisch’s 
simple apparatus (see diagram) is to be recom¬ 
mended. The filtrate to be evaporated is placed 
in a flask provided with a doubly perforated 
caoutchouc cork carrying two bent tubes; the 
tube b terminates near the bottom of the flask, 
while the tube a terminates a little above the 
level of the fluid to be evaporated. The tube a 
is connected with a water pump which sucks away 
the escaping steam. In order to avoid the run¬ 
ning back of the condensed water forming in the 
cooler part of the tube, the end of the tube a is 
twisted into a circular form. Through the tube b, 
which has a fine capillary bore, a stream of air is allowed to enter, 
which keeps the fluid in constant agitation, continually destroying the 
scum on the surface, and avoiding sediments collecting at the bottom, 
which may cause fracture of the flask. According to the regulation 
of the air current, a greater or smaller vacuum can be produced. The 
fluid, evaporated to the consistency of a syrup, is treated with 96 per 
cent, alcohol, filtered, and the filtrate precipitated with lead acetate. 
The lead precipitate is filtered off, the filtrate evaporated to a syrup, 
and the syrup again treated with 96 per cent, alcohol. This is again 
filtered, the alcohol got rid of by evaporation, water added, the lead 
thrown down by SH 2 , and the fluid, after the addition of a little hydro¬ 
chloric acid, evaporated to the consistence of a syrup; this syrup is 
exhausted with 96 per cent, alcohol, and precipitated with an alcoholic 
solution of mercury chloride. The mercury precipitate is boiled with 
water, and by the different solubility of the mercury salts of certain 
ptomaines some separation takes place. If it is suspected that some of 
the basic toxines may have been separated with the lead precipitate, 
this lead precipitate can be decomposed by SH 2 and investigated. “ I 
have only ” (says Brieger) “ in the case of mussels been able to extract 
from the lead precipitate small quantities of ptomaines.” 
The mercury filtrate is freed from mercury and evaporated, the 
excess of hydrochloric acid being carefully neutralised by means of soda 
(for it must only be slightly acid) ; then it is again treated with alcohol, 
