§ 37-1 PROCEDURE IN SEARCHING FOR MINERAL POISONS. 53 
In the method of Woehler and Siebold, the matters, suitably divided, 
are heated in a porcelain dish with their weight of nitric acid until 
a homogeneous mass has been obtained, then the acid is neutralised, 
by soda, potash, ammonia, or lime, and evaporated to dryness. The 
product is now cast in small portions at a time into a porcelain crucible 
brought to a dull red heat. The ultimate mass, which should be of a 
pure white colour, is then dissolved in boiling water and a solution 
obtained absolutely free from organic matter. According to A. Gautier, 
this method should not be used in researches on arsenic, the loss of 
arsenic being considerable. 
Basic method. —In this method the organic matters, intimately mixed 
with half their weight of pure lime or pure magnesia, are burned up in 
a muffle, and the product treated with nitric or hydrochloric acid until 
dissolved. The process has been used in researches on malt and on 
coal, no arsenic is lost, and it is suitable for toxicological investigations. 
J. Ogier’s method A—The organic matter (viscera, e.g .) is finely 
divided and made into a soupy mass by the addition of water, and 
introduced into a large flask ; about of the weight of the organic 
substance of potassic chlorate is added. Hydrochloric acid gas produced 
by the action of pure sulphuric acid on pure hydrochloric acid is passed 
through the liquid, the gas finally escaping, being led through a little 
water to arrest possible traces of arsenic chloride. As soon as yellow 
vapours are seen above the liquid the current of gas is stopped, the 
process of destruction going on now without further assistance. The 
end of the reaction is indicated by the yellow colour of the liquid. The 
insoluble matters are filtered off, and, if desired, may be treated by one 
or other of the dry methods ; but it can be shown that, as a rule, they 
are destitute of poisonous metals. The destruction is rapid, 500 to 
1000 grms. of organic matter being destroyed within the hour. 
A. Villiers ’ 2 method. —Yilliers uses the salts of manganese. The 
substances, made into the consistence of porridge by the addition of 
hydrochloric acid diluted with from 2-3 times its volume of water, are 
introduced into a suitable flask, which has a cork carrying a funnel 
provided with a stopcock and a tube, the end of which dips into water. 
Through the funnel is gradually introduced a solution of a manganese 
salt and a little nitric acid, a regulated heat being at the same time 
applied ; the gases evolved are nitrogen and carbon dioxide, hence the 
products are without odour ; the process is even more rapid than that 
of Ogier. In researches for arsenic it is obviously necessary to take 
accurately weighed or measured quantities of the reagents, and, if arsenic 
is found, to make with equal quantities of the reagents a blank ex¬ 
periment for the purpose of ascertaining their freedom from arsenic. 
1 Traile de chimie toxicologique, Paris, 1899. 
2 Com ft. Rend,, 1896, 
