Pliosphatic Materials used for Ar/ricidtural Purposes. 3G7 
of lime and likewise more alkaline salts than others: We must 
not, therefore, expect to find always in the richest samples the 
highest percentage of carbonate of lime, &c., nor in those poor in 
bone-earth necessarily a correspondingly low percentage of the 
last-mentioned constituents. But, generally speaking, a higher 
percentage of carbonate of lime and alkaline salts will be found 
in good samples of bone-ash than in those that are inferior. 
This we may naturally expect, for as pure bones contain a cer- 
tain amount of carbonate of lime, &c., the less sand a sample of 
bone-ash contains, and the more perfectly the bones are burned, 
the more phosphate of lime and likewise the more of all the 
other incombustible constituents it necessarily must contain. 
On the other hand, if bones are imperfectly burned and con- 
taminated with much sand, they naturally must yield an ash 
which is not only poorer in phosphates but in all the ash- 
constituents of bones. At all events, bone-ash must contain 
jnore bone-earth and more carbonate of lime and other mineral 
matters than the bones which furnished the ashes. 
In commercial analyses, however, the proportions of carbonate 
of lime, &c., are frequently stated to be far smaller than can be 
the case. This mistake arises from the faulty determination of 
the bone-earth. When determined in the usual way, the precipi- 
tated bone-earth invariably contains a good deal of carbonate of 
lime. The phosphates are therefore given higher than they are 
in reality, and, as it is usual to determine the rest of the lime 
which is not united with phosphoric acid and the alkaline salts 
together by diflerence, the latter constituents are consec{uently 
stated too low. 
Thus an analysis lately brought under my notice gives the 
composition of a sample of bone-ash as follows : — 
Charcoal 2-1 
Sand 4-3 
Water 3-8 
Carbonate of lime 1*9 
Phosphate of lime 87"9 
100-0 
bone-ash, gives the 
3-00 
3-00 
3-90 
.. 84-84 
.. 5-2G 
100-00 
In both analyses the amount of phosphate of lime is given too 
high, and that of carbonate of lime and alkaline salts too low. 
Another chemist, who analysed the same 
following results : — 
Moisture 
Carbonaceous matter 
Siliceous matter 
Phosphate of lime 
Cavboiiate of lime (4-48) &c 
