RESEARCH FOR ARSENIC AND ANTIMONY. 
233 
surface of the copper used, and the method of testing the 
acid and copper first pointed out by Reinsch. As a general 
rule, this is quite sufficient. There is no liability to fallacy 
unless the copper is used on a large scale, and there is an 
acid or salt present which acts upon and dissolves the impure 
metal. Pending its solution, the atoms of arsenic, combined 
with it as arsenide or arseniuret, are set free, and may thus 
attach themselves to the clean surface of the undissolved 
copper. It is clear that if the presence of a minute quantity 
of arsenic in copper presents that great risk of fallacy, 
which some chemists have recently endeavoured to impress 
on the public mind, no one of the numerous analyses for 
arsenic by Reinsch’s process, which have been undertaken 
during the last twenty years, could have been made without 
the inevitable discovery of arsenic. In short, if a source of 
fallacy, it would have led to the constant and inevitable dis¬ 
covery of arsenic in every solid and liquid submitted to 
examination. Analysts who have had much experience in 
the use of this process, will bear me out in the statement, 
that in employing samples of the same copper and acid,—for 
one affirmative result in which arsenic is discovered, there 
will probably be four or five negative results, in which no 
deposit whatever has taken place on the arsenical copper, and 
no arsenic was detected. By boiling successive quantities of 
the same arsenicated copper in the same acid liquid con¬ 
taining arsenic, the whole of the free arsenic is finally 
removed ; the deposits on the metal become less and less de¬ 
cided, they at length cease altogether, and the last portion of 
copper put into the liquid comes out nearly as bright as when 
introduced, or if at all dull on the surface, this dulness arises, 
not from arsenic, but from oxidation, as a result of lono* 
boiling. It is obvious, that if the arsenic came from the 
copper itself, and not from any extraneous source, instead of 
the arsenic diminishing on each introduction of the copper, 
it would go on increasing in proportion to the quantity of the 
metal employed in the analysis. The hundreds of negative 
results which have been obtained by experienced analysts, 
establish the untruthfulness of the assertion, that the process, 
as it is commonly employed, is attended with a serious risk 
of fallacy, even when copper containing arsenic is unknow¬ 
ingly used. The analyses performed by Reinsch, Gaultier 
de (Jlaubry, Orfila, Christison, Maclagan, Geoghegan,Watson, 
Rev, Penny, and others, are as unassailable on this ground 
ever may have been the motive animating these critics, their statements, as 
it will be seen from tlie authorities quoted, displayed either great ignorance 
or great untruthfulncss. 
