1902] TOXIC PROPERTIES OF COPPER COMPOUNDS 39 
agents capable of uniting with more chlorin.*3 That the for- 
cing back of the ionization of these double salts to the molecular 
form (e. g., K,CuCl,) would result in a lowering of its toxic value 
seems more. than probable, in view of what we know in the 
analogous case of the double salt K, HgCl, already referred to, 
and furnishes a very reasonable hypothesis to account for the 
remarkable lowering of the toxic value of solutions of copper 
in pure water when a chlorid is added in excess. The decrease 
from the adding of sulfates, nitrates, etc. of the alkali bases is 
doubtless due to similar conditions. ~ 
fig. 4 gives the results of a test Of various soluble and 
insoluble copper compounds with three fungi grown in beet decoc- 
tion. The letters A, G, and B refer to Aspergillus, Gido- 
cephalum, and Botrytis respectively. Beet decoction has a very 
marked power of dissolving copper even in the metallic state, 
hence it was possible to test “insoluble” copper compounds, 
such as Paris green, copper hydroxid (the form in which the 
copper is found in Bordeaux mixture), etc. This power of dis- 
solving copper is a property of almost all decoctions of vegetable 
or animal substances, some possessing it in a much higher 
degree than others. Es 
fig. 4 shows that copper, gram for gram, has much the same 
value toxicologically when added toa beet decoction, no matter 
what form of copper salt is used. The apparent exceptions to 
this are are to be accounted for by the effect of the other atoms 
and groups added. Thus the chromate salt which proved to be 
by far the most toxic compound of copper tested owes its high 
toxic value to the deadly chromium contained.* The eau 
celeste and the ammoniacal solution of copper carbonate are 
particularly fatal to CEdocephalum and Botrytis on account of 
the basic alkalis present.** (CEdocephalum is apparently very 
Sensitive to compounds containing arsenic. Perhaps it is espe- 
cially sensitive to this element, but so far as I know the point has 
not been tested. That the green arsenoid should be more fatal 
"3 DAVENPORT, C. B.: Experimental morphology 8. 1897. 
“CLARK, J. F.: Bot. Gaz. 28: 390, 396. 1899. 15 [bid. 28: 380-382. 1899. 
