BULLETIN OF THE BUSSEY INSTITUTION. 381 
to its aqueous solution. On being tested as to its alkalinity, it appeared 
that the substance neutralized as much standard acid as would be 
equivalent to 51.25 pounds of pure dry carbonate of potash for every 
hundred pounds of the material. In the spring of 1874, this sub- 
stance was offered at retail in Boston for three cents per pound, a price 
that was manifestly too high, in so far as the real potash was concerned, 
since it made the pound of that ingredient come to nearly seven cents 
at a time when it could be bought in Boston at 53 cents in the form of 
muriate of potash, as has just been shown. 
The proportion of potash in the prussiate residues is naturally sub- 
ject to considerable variation. ‘Thus a sample offered in the spring of 
1874, by a New York dealer in fertilizers, Mr. George E. White, of 
160 Front Street, contained d4%, of real potash, according to the certif- 
icate of a chemist of that city ; and, since the article was sold at 23 cents 
per pound, it appears that the pound of real potash would have cost 
in this form a trifle more than five cents. ‘That is to say, but little 
more than it would have cost in the form of muriate of potash, for the 
price of the 80% muriate at that time in New York was 2} cents per 
pound, which is equal to five cents per pound for real potash. 
As a matter of course, rather more care would be required in using 
a substance such as this, which contains a soluble sulphide, than would 
be needed for the successful application of the better kinds of Stassfurt 
fertilizers. ‘The farmer would have to be upon his guard lest the 
poisonous ingredient should actually harm his crop. The prussiate 
residues are well adapted, however, for composting peat, and, at least as 
regards the sample examined in this laboratory, could do no harm 
when applied in moderate doses to plough-land some days before any 
seeds were to be sown. ‘The small amount of sulphide which the 
fertilizer contains would be quickly destroyed in the earth, through 
oxidation and by the action of carbonic acid from the air and the soil. 
It is possible that in some cases the sulphide of the prussiate residue 
might be made to serve a useful purpose in destroying weeds, insects, 
or fungi; and it might sometimes happen that on this account the 
farmer would be justified in giving the preference to the prussiate 
residue over another fertilizer equally rich in potash. This remark 
would probably apply with greater force to a certain by-product which 
occurs in the manufacture of the purest cyanide of potassium for elec- 
troplaters’ use than to the prussiate residues above described. These 
