30 BULLETIN OF THE BUSSEY INSTITUTION. 
of potassium, after the liquor had been evaporated to dryness with ferric 
nitrate, and ignited to decompose the latter (see this Bulletin I., 195). 
The sulphuric acid was removed by means of chloride of barium in every 
instance, and the excess of baryta was got rid of in its turn by means 
of carbonate of ammonia. 
By using nitric acid to decompose the organic matter, all risk of 
losing either phosphoric acid, or potash through volatilization, when pre- 
paring ashes, is done away with. Compare Vol. I. p. 199. The idea 
of using nitric acid for this purpose is not new. It has been thus applied 
by Margeraff, John’s ‘‘ Ernahrung der Pflanze,’’ p. 21; by Sorby, ‘ Philo- 
sophical Magazine,’’ 1847, 830. 330; by Caillat, ‘‘ Comptes Rendus,’’ 1849, 
29. 137; by Arendt, in his ‘*‘ Wachsthum der Haferpflanze,’’ 1859, p. 29, 
and doubtless by others. 
Silica, lime, and oxide of iron, &c., were determined according to the 
usual methods in the ashes of the several materials, special portions of 
ash having been prepared for the purpose by burning the substances in 
a mufile. 
I am indebted to my assistant, Mr. J. Andrew Henshaw, for most of 
the analyses recorded in this paper. 
It appears from the foregoing analyses, that, in the case of tan, there 
is about as much phosphoric acid in a given weight of spent bark, as 
there is in the bark which has not been leached; that a considerable 
amount of the original potash is washed out, together with the tan- 
ning materials; and that the proportion of nitrogen remains essentially 
unchanged. D’Arcet* found no soluble alkali whatsoever in the 
ashes of cakes of spent tan (modtes), that had been prepared for use 
as fuel. Berthier,f on examining similar cakes (mottes) of spent tan 
from oak-bark, found 12% of ash “that was obviously mixed with 
sand.” “These ashes yield only 1.6% of soluble alkalies, and are 
consequently never employed for making lyes. It is evident that 
more than half the alkaline substances in the original bark have been 
removed by the water during the process of maceration in the tan- 
pit.” In fresh tan (oak-bark), Berthier found 6% of ash, which con- 
tained 5% of soluble salts. 
In the case of finely ground logwood, less than half as much potash 
and phosphoric acid were found in the spent materials as in the fresh 
wood; while, in their ashes, the disparity is still more strongly marked. 
The proportion of lime in the ash of the spent wood is noticeably 
larger than in the other ash. 
* “ Annales de Chimie,” 1811, 79. 152. 
+t “ Annales de Chimie et de Physique,” 1826, 32. 250. 
