DETECTION OF ARSENIC IN ORGANIC MIXTURES. 221 
tages of both the tests, and at the same time avoid their 
impediments. He found that zinc possessed such a pro- 
perty, removing every trace of arsenic from an organic 
fluid, and forming an alloy from which arseniuretted hydro- 
gen could be developed with the greatest facility. To 
apply this method : — The organic liquids are to be slightly 
acidulated with nitric acid, adding about 10 drops to the 
ounce, filtered, strained through linen or muslin, and intro- 
duced into a flask with about 2 drms. of granulated zinc. 
The whole is kept boiling for half an hour, not too rapidly, 
and the mixture is kept acid by the occasional addition of a 
drop or so of nitric acid ; during this time the arsenic will 
be precipitated on the zinc, giving it a grayish-black ap- 
pearance. The zinc is then removed, and repeatedly 
washed with boiling water to remove all organic matter. 
If the substance is solid, as the liver, intestine or muscle, it 
must be previously cut up into small pieces and placed in 
a porcelain dish, then covered with a mixture of 2 parts of 
muriatic to 1 of nitric acid, and evaporated to .dryness, 
taking care that it does not boil very rapidly ; thus the 
tissue will be destroyed and the arsenical compound con- 
verted into arsenic acid. The charred mass containing it is 
broken up, boiled in two or three successive portions of 
water, filtered, and having ascertained that the mixed 
liquids are acid, introduced into a flask with the zinc as 
above. 
The second stage of the process consists in introducing 
the zinc with some dilute sulphuric acid into an apparatus 
modified from that of Marsh. It differs from the latter in 
the lower curved portion being again curved in the centre, 
but in the opposite direction, thus forming an undulating 
portion consisting of three curves in the same plane, the 
two lateral of which have the convexity directed down- 
wards, that of the centre being upwards. Near the summit 
of the longer limb, as usual, there is a bulb ; the shorter 
limb has two bulbs, one large and close to the bottom, the 
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