1872.] Dr. A. W. Hofmann on the Phosphorus Bases. 



229 



crystals thus produced, which could not be obtained in distinct forms, are 

 hygroscopic but not deliquescent. They readily dissolve in water, the so- 

 lution restoring litmus red to blue, and possessing, moreover, an agreeable 

 sour taste. They are also soluble in alcohol, less so in ether ; the alcoholic 

 solution, however, is not precipitated by ether. The stability of this body 

 is quite remarkable ; that it is not altered by fuming nitric acid is evident 

 from the manner of its preparation ; but even by repeated evaporation with 

 aqua regia not the slightest change is produced. 



The new compound melts at 105° C. ; it is volatilized, at least for the 

 greater part, without decomposition ; when strongly heated, it evolves an 

 inflammable gas, a small residue of phosphoric acid mixed with more or 

 less carbon remaining behind. 



Analysis showed that methylphosphine, by treatment with nitric acid, 

 fixes three atoms of oxygen, the composition of the new body being repre- 

 sented bv the formula 



CH.PO,=(CH,)H,PO,. 



The new substance is a well-marked acid ; I will designate it by the 

 name placed at the head of the paragraph, i. e. monomethylphosphinic acid, 

 or more briefly methyl phosphinic acid. It forms two series of salts, the 

 composition of which is represented bv the formulae 



(CH 3 )HMP0 3 and (CH 3 ) M 2 P0 3 . 



The primary (acid) salts are produced by the action of metallic car- 

 bonates, or by incomplete saturation with the free bases. For the pre- 

 paration of the secondary (neutral) salts, the acid must be completely satu- 

 rated by the free bases ; they can, however, also be obtained by means of 

 carbonates, if the latter, as is the case with the alkaline carbonates, are 

 capable of fixing the carbonic acid which is liberated. 



The primary methylphosphinates have an acid, the secondary salts an 

 alkaline reaction"* these latter are soluble and only little inclined to crys- 

 tallize. The ammonium-salts lose ammonia by evaporation, leaving the 

 acid behind. Amongst the metallic salts, especially the primary ones, 

 many are insoluble, or soluble only with difficulty. 



Silver Methylphosphinate. — If the acid be saturated with silver oxide 

 and the solution evaporated to the consistence of a syrup, the primary salt 

 separates from the solution in beautiful white needles, which, in contact 

 with water and even with alcohol, are readily converted into the secondary 

 salt with separation of the free acid. 



The salt obtained by means of silver oxide and purified by washing with 

 water gave numbers which showed that it consisted of the nearly pure 

 secondary compound. In order to obtain this salt quite pure, the solution 

 of the acid was accurately neutralized by ammonia and precipitated bv 

 silver nitrate. It is a white amorphous precipitate, nearly insoluble in 

 water, having the composition 



CH 3 Ag 2 P0 3 . 



Lead Methylphosphinate. — If an aqueous solution of metliylphosphinic 

 vol. xx. s 



