BULLETIN OF THE BUSSEY INSTITUTION. 199 
are given in the table on page 207. A glance at the figures of that 
table will show how small the average proportion of phosphoric acid 
in the New-England ashes really is, see page 193, as compared with 
what we have hitherto had reason to believe. 
From the statement of the actual analytical work that has been 
given already, it will be seen that pains were taken to control the esti- 
mations of phosphoric acid in such manner that the fact of the small . 
proportion of this substance in household ashes should be established 
beyond all chance of doubt. On the other hand, I have satisfied 
myself by a critical examination of many of the analyses reported by 
previous observers that their results also are generally correct. ‘There 
is no occasion to doubt that carefully prepared samples of wood-ashes 
really contain as much phosphoric acid as the published analyses have 
indicated. 
The reason why there is less phosphoric acid in ashes obtained from 
domestic fires than in ashes that have been made on purpose for analy- 
sis, doubtless depends upon the circumstance that the household ashes 
have not been “carefully prepared.” It is plain that when wood is 
burnt in an ordinary stove or fireplace, for the sake of evolving heat, 
some part of the phosphorus compounds in the wood must inevitably 
be exposed to conditions that are unfavorable for the retention of 
phosphates in the ashes. There can hardly fail to be conditions in 
some parts of the fire that are favorable for the destruction of phos- 
phates, either by simple removal of oxygen by hot carbon or carbonic 
oxide, as in that process of making phosphorus where an acid phos- 
phate is heated with charcoal, or by the combined action of silica and 
carbon, as in Weehler’s method of preparing phosphorus. 
It was pointed out long ago by John * that the phosphates contained 
in plants might be partially decomposed by the action of carbon in the 
preparation of ashes. At a later period, Erdmann f was at pains to 
cited) found 6.55% potash, 2.84% phosphoric acid, 18.79% carbonic acid, and 
84.80%, of sand, clay, and charcoal in the fine part of a sample of commercial 
ashes that seemed to him to be very impure. The original ashes from which 
those analyzed by Wicke were sifted left 34.85% of charcoal and other coarse 
materials upon the sieve. These three samples were from different parts of 
Germany. | 
* In his “ Ernihrung der Pflanzen,” Berlin, 1819, pp. 152, 153. 
t “Annalen Chemie und Pharmacie,” 1845, 54. 358 ; further * Journal fiir 
praktische Chemie,” 31. 17 and 39. 276. 
