392 BULLETIN OF THE BUSSEY INSTITUTION. 
potashes at their present low price. However that may be, there is 
little reason to doubt but that the Stassfurt fertilizers admixed with 
lime would be found to be better fitted for making compost than the 
common ‘salt and lime mixture” which has been so much used in 
New England and in the Southern States. The sulphate of potash in 
particular, of tolerably high grade, would seem to be much better suited 
for this purpose than common salt. 
As is well known, the salt and lime process consists in slaking 
quicklime with brine, and mixing the slaked lime with peat or with the 
other organic matters that are to be composted. One way of proceed- 
ing is to dissolve a quantity of common salt in water, and to slake 
the quicklime with as much of this brine as would bring the lime 
to the condition of fine powder. The powdery slaked lime is then 
spread, while still warm, between layers of the peat. The efficiency 
of the salt and lime mixture doubtless depends, as Professor Johnson 
has urged in his “ Peat and its Uses,’ New York, 1866, p. 74, upon 
the unequal rates of diffusion of the chemical substances which either 
exist originally in the lime and salt mixture, or which may be formed 
from it under the conditions that obtain in the compost heap. Small 
quantities of caustic soda and chloride of calcium are doubtless formed 
under these conditions, and are carried into the moist peat in accord- 
ance with the laws that govern the diffusion of liquids. The peat, 
or a part of it at least, is thus exposed to the powerful action of the 
soluble alkali soda, and of the carbonate of soda into which the hydrated 
soda at first formed is soon converted, and on that account the organic 
matter undergoes a more rapid and complete decomposition than would 
be brought about by the lime alone. It is plain, however, that the use 
of salt in this way is merely a clumsy device for adding a small propor- 
tion of soluble alkali to a lime compost. The process amounts to no 
more than adding a little soda ash to the lime. But as Graham* has 
been at pains to show, in his researches on the diffusion of liquids, the 
potash salts, as a rule, exceed those of soda in diffusibility. Hydrate 
of potash in particular is an eminently diffusive substance, having 
double the diffusibility of sulphate of potash. Graham found in fact 
that sulphate of potash was decomposed to a marked extent by lime 
* “Philosophical Transactions of the Royal Society,” London, 1850, 140, 21; 
1851, pp. 484, 494. “ Quarterly Journal Chemical Society of London,” 1851, 
3. pp.61-67. 
