Metals and Plants. 
467 ' 
so. The salts of the elements standing high in the above series 
which did not kill our plants are, so far as known, compara¬ 
tively harmless. On the whole, this series is strikingly simi¬ 
lar to the one we would make from the effects upon plants. 
On the second factor — the toxicity of the salts of the sev¬ 
eral elements—there is considerable more or less instructive 
but scattered literature. On platinum and gold the only infor¬ 
mation we have found, is a statement by Knop (10. Ref.) that 
PtCl 4 and AuC 1 3 are injurious to plants, without being de¬ 
monstrable in the ash; which indicates that they are extremely 
poisonous. The same statement is made with regard to Ag 2 O. 
Kahlenberg and True (9. p. 104) find the salts of silver to be- 
the deadliest they used, 
N 
• being about a sufficient concen- 
409,000 
tration to kill lupines in one day. According to Paul and 
N 
Kroenig(20), of silver salts is necessary to kill nearly all 
bacteria in a culture in 10 h. 30 m. The same authors find gold 
more toxic than copper, but do not call platinum very injur¬ 
ious. Kahlenberg and True state that lupines will just live in 
N 
12 800 Cl 2 : but Heald (8) places the limit of endurance for 
N 
Fisum sativum at ————: and Paul and Kroenig for bacteria, 
204,800’ 6 * 
and Stevens (27) for fungus spores, agree that mercuric salts 
are among the most poisonous known. Other experiments with 
palladium are not known, but our own merely qualitative one 
(Table III) showed that its salts are very poisonous. Among 
these first five metals of our tables, then, are those whose salts 
are the most deadly known; and yet, because of their resistance 
to corrosion, their presence in the free, native state caused lit¬ 
tle or no injury. 
From the appearance of the metal and from its position in 
Neumann’s table, it is probable that considerable aluminum 
went into solution; and from its not hurting the plants, we con¬ 
clude that it is not very poisonous. This conclusion is con¬ 
firmed by Molisch (16) who applied alumium sulphate in con¬ 
siderable quantities to pots of Hortensia without very great in- 
