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XX III. Notice of a new Hydrated Phosphate of Lime. 

 % John Percv^, M.D.* 

 nj^O a solution of common phosphate of soda, in a large quan- 

 A tity of distilled water, add a solution of chloride of calcium 

 till precipitation ceases. Immediately pass through the mix- 

 ture, containing the phosphate of lime suspended, a current 

 of carbonic acid gas, and continue this for about an hour; 

 then filter immediately, and set aside the filtered liquor in a 

 jar, the mouth of which is covered loosely with paper to keep 

 out dust. In the course of a day or two, and sometimes in a 

 much shorter time, crystals will appear on the surface, and 

 will, when stirred with a rod, sink. After the lapse of several 

 days a very sensible quantity of crystals may be collected. 

 Transfer them to a filter, and wash with cold or tepid distilled 

 water, and dry in a ivai-m place. 



It occurs in the form of brilliant white scales, which, on 

 examination with the microscope, are seen to consist of modi- 

 fied rhomboidal plates more or less broken and confused. 



The salt melts with difficulty at an intense heat by the 

 blowpipe on platinum foil. Heated to bright redness in a 

 platinum crucible, 3*21 grs. of salt lost 0*85, and in a second 

 experiment 'A-16 grs. lost 084 gr. I found that every trace 

 of water was given off' after exposure for 10 minutes or a 

 quarter of an hour to a bright red heat. 



Rose's plan was followed in determining the lime and phos- 

 phoric acid, which consists in dissolving in hydrochloric acid, 

 then adding sulphuric acid, then alcohol, which precipitates 

 the lime completely as sulphate. 



I. 3'21 grs. of salt gave 2*51 of sulphate of lime. 



II. 3-16 grs. ... 2-48 



Taking 28 as the equivalent of lime, and phosphoric acid as 

 72, we have — 



First analysis. Second analysis. 



Water 0'85 0-84 



Lime 1-04 1-02 



Phosphoric acid . . 1-32 1-30 



3-21 3-16 



The oxygen of the water is three times as much as that of 

 the base, and the salt agrees in composition with the formula 

 2CaO + PO5 + 6HO. 

 The rational formula will, doubtless, be HO, 2CaO, PO5 

 + 5HO, 1 equiv, of water being basic and 5 constitutional. 



2*40 grs. of this phosphate heated in the oil-bath at a tem- 

 perature between 134° and 148° centig., lost 0*30 gr. in l^ 



* Communicated by the Chemical Society ; having been read November 

 18, 1844 



