METHOD! OF OBTAINING PHOSPHORIC ACID.

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glass jar, one pound of sulphuric acid with six or eight pounds ofwater; then add gradually, and with constant stirring, onepound and a half of finely pulverized bones burnt to whiteness.An effervescence will take place. When this has ceased leavethe whole on a gentle sand-bath for a few hours, taking care tostir it frequently, and to supply the loss of water which happensby evaporation. After it has been suffered to remain undisturb-ed, strain the whole through a cloth, and wash' the residualmatter repeatedly in water till it passes tasteless. The fluid thusobtained contains the phosphoric acid, contaminated with lime,and may be evaporated in a Wedgwood’s, or glass bason, to anywished-for consistence.

Remark. ..The phosphoric acid obtained in this manner is notpure, but contains a considerable quantity of lime. To obtainit in its pure state, carbonate of ammonia must be added untilno more precipitate falls down, the precipitate is carbonate oflime, which must be separated by filtration; the fluid being thenevaporated to dryness leaves phosphate of ammonia. This isexposed to heat in a china cup, till all the ammonia is disen-gaged, which may be known by the mass frothing no longer,but flowing quietly. On cooling, it congeals into a transparentvitreous substance, called glacial acid of phosphorus, which at-tracts moisture, and is soluble in water.

2. Phosphoric acid may likewise be obtained by the rapid orcomplete oxigenation of phosphorus, by burning it in oxigengas, as mentioned before, vol. I. p. 188.

3. Scheele has contrived a method of converting phosphorusinto phosphoric acid-without combustion; namely, by the actionof nitric acid.

In this operation a tubulated glass retort must be half filledwith pure nitric acid, and a gentle heat applied. A small pieceof phosphorus being then introduced through the tubulure willbe dissolved with a rapid effervescence, and a quantity of redvapour will be disengaged. The addition of phosphorus in smallpieces must be continued until the last piece added remains un-

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