68 REPORT—1858. 
salt in the form of brilliant bronze-coloured scales, strikingly resembling the bronze- 
coloured mica of some granites. This salt contains sulphuric acid; but whether all 
the chrome exists as chromic acid, J have not yet ascertained; I have failed in 
reproducing it. 
3. I treated a boiling concentrated solution of bichromate of potash with glacial 
phosphoric acid and set it aside until the following day; a pale orange-red salt ery- 
stallized out in small nacreous scales. A portion of this salt, dissolved in water and 
set aside to crystallize, yielded a beautiful salt consisting of well-developed rectangu- 
lar prisms of remarkable brilliancy. One feature of the action of phosphoric acid 
was, that the solution, no matter how much of the glacial acid was added, did not 
deepen in colour: it rather indeed became paler, and at no time did there appear to 
exist any uncombined chromic acid in solution. 
On the Constitution of the Mineral Portion of Bones, and the Analysis of 
Common Bone-ash, Animal Charcoal, 5c. By Professor VoELCKER, 
PAD. FCS. 
Heintz of Berlin maintains the phosphate of lime to exist in a tribasic form, but 
found in human and other bones an excess of lime, combined neither with PO® nor 
CO?. This he regards as fluoride of calcium, and consequently records as much as 
3°85 per cent. of that substance as existing in bones. This, however, is simply the 
result of calculation from the excess of lime. The author had made many experi- 
ments to determine fluoride of calcium in bones, but without success; although when 
he added 1 per cent. of that substance to pure phosphate of lime, it could be readily 
determined. 
When a dilute acid solution of bone-ash is precipitated by ammonia, the author 
has always found as much lime as is contained in the tribasic salt, and usually more, 
as carbonate of lime will be found to fall down with the precipitate in spite of all 
precaution; this is especially the case when the precipitation has been accompanied 
by heat. When conducted in the cold, and reprecipitated, the result agrees very closely 
with tribasic phosphate. In proof of the discrepancies of the process of precipitation, 
are the following experiments :— 
I. Il. 
1. Bone-ash gave precipitated phosphates . 75°84 73°29 
2s LS ene, ke 79°03 
Animal charcoal gave— 
Furst: precipitation 5 2s). <) 14.) ..ce, fh pCi 
Dissolved and reprecipitated . . . . « 73°63 
Re-dissolved a e fy ae he ie Pelae 
The direct determination of phosphoric acid gave 33°34=tribasic phosphate 72°23 
per cent. The author much regretted the discredit brought upon chemistry by the 
great variations in commercial analyses of these substances, and alluded to a practice 
adopted by some chemists of regarding the precipitate as 8Ca0+3PO', and after- 
wards re-calculating the phosphoric acid into the tribasic salt, by which their results 
became much too high. He considered it imperative to discard the precipitation pro- 
cess altogether, and to state the amount of phosphoric acid actually found, giving the 
per-centage of tribasic salt equivalent to this. 
The author recommends the following plan for the commercial analysis of bone-ash, 
animal charcoal, &c., and has employed it for some time in his own laboratory. 
Moisture and organic matter are determined as usual. About 20 grains are dissolved 
in nitric acid, and the solution evaporated on a water-bath to dryness, which effects 
the conversion of any pyrophosphate into ordinary phosphate. The residue is taken 
up by the smallest possible quantity of nitric acid, then diluted with water, the sand 
removed and the solution filtered. This is precipitated by excess of oxalate of potash, 
and before removing the resulting precipitate, the liberated oxalic acid is nearly neu- 
tralized by potash, acetate of potash is added, and the whole boiled. By this means 
the oxalate of lime held in solution by free acid is thrown down. Filter and wash the 
precipitate, and concentrate the filtrate to a small bulk. Add a little tartaric acid to 
keep in solution any iron or alumina, and precipitate the phosphoric acid by ammoniacal 
sulphate of magnesia: after standing for twelve hours, filter, partially wash the preci- 
