382 BULLETIN OF THE BUSSEY INSTITUTION. 
cyanide residues are said to be bought and sold in considerable quanti- 
ties in New York at cheap rates. They are obtained from the mother 
liquors whence pure cyanide of potassium has been separated by crys- 
tallization. They are said to contain a high percentage of potash 
(more than 50%), and to be used by the makers of fertilizers as a 
means of putting potash into their wares. Such residues would prob- 
ably almost always contain more or Jess cyanide of potassium, which, 
as was just suggested, might sometimes be used with advantage for 
destroying noxious insects, or perhaps plants. Once mixed with the 
soil, it would soon lose any cyanide of potassium that may have been 
contained in it, since that compound would be decomposed, and made 
harmless by the action of carbonic acid. As regards the practice of 
mixing the cyanide residues with other commercial fertilizers, for the 
sake of introducing a certain amount of potash, the practice would 
seem to be safe enough in so far as concerns the superphosphates ; for 
the soluble phosphoric acid of a true superphosphate would quickly 
decompose any cyanide of potassium with which it came in contact, as 
it would the alkaline sulphide in a prussiate residue. But when mixed 
with most kinds of commercial manures, other than the true super- 
phosphates, the cyanide residues would undergo no such purification : 
they would be simply concealed in the mixture, and from the very fact 
of their concealment would be more likely to do harm than when used 
by themselves. This remark illustrates one general objection to the 
custom of buying mixed manures, which seems to be gaining ground 
in this vicinity. ‘There are many reasons why the farmer should as a 
rule buy his potassic, phosphatic, and nitrogenous fertilizers separately, 
and judge for himself as to the proportion in which each should be 
used upon any given farm or field; and not least among these reasons 
is the security which is gained of knowing the character of each of the 
materials with which he means to deal. There is little risk in applying 
any manure whose attributes are clearly understood, and of the sub- 
stances now in question it may be said that the peculiarities of both 
are palpable. It would be easy to recognize either the prussiate resi- 
due or that from the cyanide so long as the residues were kept by 
themselves ; but when mixed with other fertilizers it might be hard to 
detect them, and it would usually be very difficult to judge of the 
amount of either of them that the mixture contained. It may be 
remarked in this connection that much harm has actually been done in 
