206 BOTANICAL GAZETTE (MARCH 
toxicity of toxic waters and salt solutions, and that of colloidal 
platinum, gold, and silver upon the toxicity of NaOH may be con- 
sidered as probably due to surface phenomena such as adsorption. 
It appears from the experiments that ionic gold and ionic platinum 
(AuCl, and PtCl,) exerted no influence upon the toxicity of NaOH 
and MgSO,, respectively. The information at hand is not sufficient 
to warrant any suggestion as to why the transfer of filaments from 
colloidal gold solution to non-toxic distilled water was so quickly 
fatal to Spirogyra. A possibly similar case, in which the toxicity 
of a solution was decreased by addition of a colloid, has been 
reported by HatcHer (7), who found that the toxicity of strychnine 
injected hypodermically into frogs and guinea-pigs was consider- 
ably decreased when the alkaloid was administered in a solution of 
gum acacia. In this connection it needs only to be suggested that 
the finely divided and otherwise highly absorbent solids which, as 
has been shown by various authors since the time of N ageli 
(NAGELI 14, TRUE and OGLEVEE 15, BREAZEALE 1, LIVINGSTON éf 
al. 11, LIVINGSTON 12, JENSEN 9, Hoyt 8), exert a correcting influ- 
ence upon many toxic solutions, partake of some of the properties 
of colloids. One essential feature, in this regard, of all such solids, as 
well as of both suspensoids and emulsoids which exert such correct- 
ive influence, seems to be great extension of surface. 
It is interesting to notice that, although colloidal platinum pro- 
duced improvement in ordinary distilled water, a weak solution of 
agar, when added to such water, produced no improvement. It 
has also been pointed out in another paper (8) that a 1 per cent agat 
hydrogel made with this water was found to be only slightly toxic, 
while a similar 2 per cent agar hydrogel was decidedly injurious. 
Evidence is not at hand for any attempt to interpret these phe- 
nomena critically. 
The results obtained furnish no indication as to what physico- 
chemical properties may be ascribed the extreme toxicity of colloidal 
silver and copper when colloidal gold and platinum are so slightly 
injurious. These results agree with those obtained by FoA and 
AGGAzzoTti (5), who showed that, although colloidal platinum, 
gold, and silver were about equally effective in hindering the 
development of bacteria, colloidal platinum and gold in strengths of 
