368 BULLETIN OF THE BUSSEY INSTITUTION. 
ily in the retort, so that it can be drawn off in the fluid condition 
when the distillation is finished. By roasting the cake in due 
course it is no very difficult matter to drive off the excess of sul- 
phurie acid and obtain a neutral sulphate of potash eminently 
proper for agricultural use. The excess of acidity might have been 
mitigated withal by mixing the cake with bone-black or with leached 
ashes, or by using the material on land that had recently been 
limed. But, as was just intimated, certain manufacturers neglected 
at one time to roast their cake, and they sold the acid, corrosive 
product to be used directly as a manure, whereby no little harm 
was done through the destruction of seeds and young plants with 
which the substance came in contact. My attention was called to 
one case in particular, where a crop of tobacco was checked and 
practically spoiled when the young plants were transplanted into 
land that had been unwittingly dressed with this material. No 
doubt this acid sulphate might be used with advantage in certain 
cases, as an ephemeral agent of destruction, 7. e. for cleansing land 
that is overrun with weeds or infested with insects or worms; and 
a solution of it might be used for composting weeds, with the view 
of killing their seeds. But the farmer needs to know what the ma- 
terial really is, so that he may either avoid it or use it with due 
care. It is manifestly unfit for general use, and should never have 
been sold as ‘‘ a manure.” 
The sensitiveness of many plants to acids, as illustrated by this 
example, and by numerous instances that are on record where the 
soluble phosphoric acid in superphosphates, having failed to be 
speedily precipitated in the earth, has done the crops more harm 
than good, may perhaps have some bearing even on the use of the 
neutral potash-salts. For example, in case chloride of potassium 
were added toa soil that was not sufficiently charged with basic 
constituents, injury might perhaps be done to the crop by the chlo- 
rine in the pvtash-salt; for, as is well known from experimeuts 
made by way of water-culture, plants can take the potassium from 
this salt much faster and in much larger quantity than they can 
take the chlorine, so that the latter, or more properly speaking 
chlorhydric acid, may actually be set free by the action of plant- 
roots. In a properly constituted soil there would naturally be 
present an abundance of basic matters, with which the chlorine 
would combine, so that the crop would be left unscathed. But 
harm might be done if these constituents were absent. Possibly 
the presence of carbonate of lime in the soil may be a safeguard in 
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