On the Volatility of Phosphoric Acid in Acid Solutions 403 
By quantitative analysis, the mineral was found to consist of 
Phosphate of lime, . : . 92-405 
Chlorid of calcium, : ‘540 
Peroxyd of iron, ain artes ts ‘040 
of manganese, ..; . ‘ 003 
F'luorid of calcium, by difference, 7-012 
| 100-000 
f the oxyd of iron is regarded as protoxyd, it will amount to 
0-036 instead of 0-040, but the color forbids its being set down 
as the protoxyd. ‘The mineral is evidently identical with apatite. 
Boston, March 27, 1851. 
Art. XLVII.—On the Volatility of Phosphoric Acid in Arid So- 
lutions when heated ; and on Schmidt's Process for the Deter- 
mination of Nitrogen; by J. B. Bunce, of the Yale Aualyti- 
‘cal Laboratory. Communicated by Prof. J. P. Norton. 
1. On the Volatility of Phosphoric Acid in Acid Solutions. 
Rose, in a paper upon the determination of phosphoric acid, 
mentions the volatility of this acid with the vapor of water, when 
evaporated in an acid solution. The object of the following ex- 
periments, was to ascertain the extent of loss which would b 
suffered in analysis in consequence of this volatility. With this 
object in view, 544 grammes of phosphate of soda were dissolved 
in a gill of water; hydrochloric acid was then added, and the 
whole evaporated in a water-bath to dryness, being afterwards 
heated gently to drive off any excess of acid. The residue was 
treated with strong sulphuric acid, and allowed to stand several 
hours in order to convert the pyrophosphate of soda into the or- 
dinary tribasic salt. It was then diluted carefully, neutralized by 
ammonia, and precipitated as ammonio-phosphate of magnesia ; 
the weight of this salt after ignition, was ‘0701 grammes, equal 
to ‘045 of phosphoric acid. ‘The consequent loss of phosphoric 
acid in this experiment was 58-66 percent. Another experiment 
in which the chlorine instead of the phosphoric acid was deter- 
mined, gives as the loss of acid 53°36 per cent. 
‘2 srammes of phosphate of magnesia and ammonia were next 
taken, dissolved in hydrochloric acid, diluted until about a gill 
of fiuid was obtained, and the whole was then evaporated as 
before; after precipitation and ignition, the residue weighed 
1316, corresponding to 41:69 per cent. of phosphoric acid. 
