414 
MEDICO-LEGAL CONTRIBUTIONS ON ARSENIC. 
copper (Cu 68, As 32 per cent.), and that by continued 
lieating of this deposit in hydrogen gas it loses only 7 Jier 
cent, of arsenic, and that then if ignited in air the greater 
part of the arsenic remains. 
Reinsch^s test is readily made. It is not, however, so 
delicate as Marsh’s test. There are a number of objections 
to it, the most important of which are the following : 
1. If the arsenic is in minute quantity, the deposit on 
copper will not produce arsenious acid in sufficient quantity 
to make the confirmatory tests. 
2. If sulphide of arsenic is present it escapes detection 
altogether. In this state arsenic often exists in the remains 
of those poisoned by it who have been dead a considerable 
time. Arsenic is often contained in the commercial copfier, 
and hence, under certain circumstances, as when free chlorine 
is present in the liquid examined, a deposit of arsenic would 
be produced, even if the liquid did not contain it originally. 
5. Fresenius^ and Balds apparatus .—Arsenious and arsenic 
acids, and their corresponding earthy and alkaline salts, 
when ignited with a mixture of cyanide of yjotassium 
and carbonate of soda, yield up all their arsenic in the 
metallic state. If the tersulphide of arsenic be employed, 
the greater part of the metal is reduced; the remainder 
forms a sulpho-salt unacted upon by cyanide of potassium. 
If an excess of sulphur is present the metal remains in great 
part or wholly unreduced. If the ignition is made in a 
sealed glass tube, sealed at one end, a part of the arsenic 
may be oxidized by the air, and thus, if it be present in 
small quantity, it may escape detection. To avoid this 
result, Fresenius and Babo recommend an apparatus in 
which the reduction takes place in an atmosphere of carbonic 
acid. 
The flask for the evolution of carbonic acid is partially 
filled with lumps of marble or compact limestone. It is 
closed by a cork, containing two perforations, into one of 
which is fitted the funnel tube, into the other perforation is 
a tube connecting the two flasks. The second flask contains 
concentrated sulphuric acid, which dries the gas as it passes 
through it. The mode of using the apparatus is as follows : 
—The sulphide of arsenic, or preferably the arsenate of soda, 
prepared from the suspected matter as already mentioned, is 
pulverised in a warm mortar with ten parts of a well-dried 
mixture, consisting of three parts of carbonate of soda and 
one part of cyanide of potassium. The powdered mass is 
then placed on a slip of glazed card paper, bent into the 
