234 
RESEARCH FOR ARSENIC AND ANTIMONY. 
as those which have been performed by Mr. Herapath 
himself, even with his No. 13 commercial wire, i. e., 
assuming that the copper and acid have been boiled together, 
and no deposit formed before the suspected substance was 
added. 
There is, however, great danger in endeavouring to conceal 
or distort a scientific truth, especially when, as experience 
now shows, reliance is placed upon false criteria to determine 
the presence or absence of arsenic in any given sample of 
copper. In the letter already referred to, Mr. Herapath states 
that the hundredth part of a grain of arsenic contained in the 
quantity of copper gauze (ten grains) used by Dr. Odling and 
myself in one of the analyses in Smethurst’s case, would have 
rendered it (the copper) so brittle , that it could not be drawn 
into wire at all, much less into fine wire fit for gauze. The 
copper-wire (woven in gauze) which led to this fallacious 
result was not more than the 1-200th of an inch in diameter, 
and probably even less. The gauze included about 10,000 
spaces or apertures in the square inch. We had the benefit 
of the opinion of an experienced chemist (Mr. Brande) as to 
the quantity of arsenic separated from the gauze in this 
experiment; it was considered to be equivalent to a propor¬ 
tion of at least 1-1000th part of arsenic. It caused some 
surprise to Mr. Brande, as well as to ourselves, that so 
much arsenic, in a well-defined ring of octahedral crystals, 
should have been procured from such highly flexible and re¬ 
fined copper as that which we employed in our experiment. It 
was a new fact to him and to ourselves, that copper in so 
highly ductile and flexible a condition should be so strongly 
impregnated with arsenic. It is clear from Mr. Herapatfds 
reliance on exceeding brittleness as a test of the presence of a 
small quantity of arsenic in copper, that he would have drawn 
the same inference which, in the first instance, we felt con¬ 
strained to draw, namely, that no arsenic could be con¬ 
tained in a wire so fine and flexible as that which we used. 
Other authorities share Mr. HerapathT erroneous opinion 
in reference to this matter. Gmelin says, on the com¬ 
bination of arsenic with copper,* that “ copper alloyed with 
0T5 per cent, of arsenic, becomes somewhat brittle when 
cold, and very brittle at a red heat.” Regnault states, 
that copper containing arsenic in small quantity becomes 
whitish and verv brittle : and Abel and Bloxam sav, that a 
very small quantity of arsenic injures the colour of the 
metal, rendering it whitish, at the same time causing it to 
* ‘ Handbook of Chemistry/ tome v, p. 470. 
