OF ASCERTAINING THE PRESENCE OF DIFFERENT METALS. 
159 
Arsenious acid . — I mixed a small quantity of solid arsenious acid in powder, 
with the following substances, separately, viz. wheaten flour and its paste ; 
bread; cake with currants and caraway seeds; starch in powder, and in solu- 
tion ; rice in powder, and boiled with water to a pulp ; potatoes boiled, and 
roasted ; sugar in powder, and in syrup; vinegar, and raspberry vinegar; port 
and sherry wines ; gruel, thick and thin, with sugar and milk, also with sugar 
and wine ; milk and cream ; white and yolk of egg, both fluid and coagulated ; 
gelatine (isinglass) in solution ; bile discharged from the stomach, mixed with 
saliva, and watery fluid. 
In a number of those instances, it was only necessary to put a little of the 
mixture into the platina spoon, incorporate a few drops of muriatic acid with 
it, and apply a slip of zinc, when the arsenic was readily precipitated on the pla- 
tina. In cases when the arsenious acid existed only in very minute quantity, 
or when the water present was considerable, the fluid was concentrated by 
boiling, or evaporated nearly to dryness, previous to the application of the zinc, 
when the arsenic was in like manner deposited. 
Arsenious acid was also mixed with butter, lard, and oils ; some of the re- 
spective mixtures being boiled a short time in the platina spoon with muriatic 
acid, or in solution of fixed alkali, then muriatic acid added in excess, and the 
zinc applied, when the arsenic readily appeared. 
A few drops of an aqueous solution of arsenious acid were mixed with some 
sheep’s blood; muriatic acid was added ; the whole formed a deep wine yellow 
solution. A drop or two being put on the platina foil, and the zinc applied, 
coagulation took place, and the arsenic precipitated. Ox-bile being treated in 
a similar manner afforded analogous results. 
In one instance, I mixed five grains of solid arsenious acid in about half a 
pint of tea sweetened with sugar and milk. It was kept hot for some minutes, 
and occasionally stirred. A little of the tea being put into the platina spoon, 
and muriatic acid added, the application of the zinc produced no immediate 
effect. But on boiling the spoonful of tea nearly to dryness, then adding two 
or three drops of muriatic acid to the residual brown substance, and agitating, 
a yellow solution was formed. A slip of zinc being now applied, a white coa- 
gulum, which soon changed to brown, appeared, and the arsenic was copiously 
precipitated on the spoon. 
