PREPARATION OF PHOSPHORIC ACID. ^g3 



XL 



Process for preparing pure Phosphoric Acid: by Mr. 

 Martres, Apothecary at Montaubauy and Member of 

 several Societies *. 



While physicians devote their studies to the search Improvements 

 after new means of alleviating the sufferings of mankind,^" P^'^^^^^^'^y 

 it is the duty of apothecaries to second their efforts, by en- 

 deavouring to simplify or improve the preparation of medi. 

 cines. 



Dr. Lasalle, of Montauban, having employed the phos- Phosphoric acii 

 phoric acid with success in the treatment of some diseases, "''^ medici- 

 I endeavoured to supply him with it very pure, in a little 

 time, and without danger, by a process, which I have 

 found to succeed completely: being fully convinced, that 

 we cannot rely with entire confidence on preparations, that i 

 come to us in the ordinary way of trade. 



We may proceed jn six different ways, to obtain phos- Methods of 

 phoric acid ; but five of them are not very easy of execution, Preparing it, 

 and the product is almost always contaminated with phos- 

 phorous acid. 



The sixth, pointed out by Lavoisier, yielc^s a pure phos- improveJ 

 phoric acid, but exposes the operator to some danger. This ^^'^^'^*^'^- 

 therefore it is desirable to obviate; Avhich I have effected 

 by means of an apparatus, that I shall describe before I 

 give an account of my process. 



The neck of a retort, placed on a sand-heat, is to be Apparatus. 

 introduced into the mouth of a receiver, the second neck of 

 this receiver into the mouth of another, and the second 

 neck of this into a curved adopter, the mouth of which 

 opens in a vessel of water, so as to answer the purpose of 

 a tube of safety +, 



The apparatus being thus arranged, 32 gr. [494 grs.] of Process de- 

 phosphorus are to be put into the retort, through its tu- ^cnbed, 

 bulure; and an equal weight of a mixture consisting of 



* Ann. de Chim. vol. Ixxiii, p. 99. 



f The atmosplieric air expelled from the receivers by the nitrous- 

 vapours escapes from the mouth of the adopter, which may after- 

 ward be stopped. 



equal 



