230 Dr. A. W. Hofmann on the Phosphorus Bases. [Mar. 21, 



acid be boiled with an insufficient quantity of lead oxide, the primary and 

 secondary salt are formed at the same time ; the latter as a white amor- 

 phous heavy powder which collects at the bottom of the hot liquid, the 

 former crystallizing from the liquid as it cools in beautiful, long, lustrous, 

 white needles. On washing with water, the salt is decomposed like the 

 silver compound, gradually forming the secondary salt and free acid; 

 indeed analysis of the washed crystals gave numbers lying between those 

 required for the primary and secondary salts. The secondary salt may be 

 obtained, however, in a state of purity if the barium-salt presently to be 

 described be decomposed by lead acetate. It is a precipitate almost in- 

 soluble in water, but soluble in acetic acid ; its composition is 



(CH 3 )PbP0 3 , or perhaps more correctly (CH 3 ) 2 Pb 2 P 2 6 . 



Barium Methylphosphinate. — This is obtained by boiling the acid with 

 barium carbonate, evaporating the solution to the consistence of a syrup, 

 and precipitating by alcohol. It is a white powder consisting of micro- 

 scopic needles easily soluble in water. The aqueous solution, even on slow 

 evaporation, yields no crystals, but dries to a gummy mass. Analysis 

 showed the salt to be the primary compound 



C 2 H, Ba P 2 6 = (CH 3 ) 2 H 2 Ba P 2 O,. 



Methylphosphinic acid has the same composition as methylphosphorous 

 acid, but it is only necessary to compare the above statements with what is 

 known respecting the latter compound in order to see that they constitute 

 two absolutely different bodies. Methylphosphorous acid is an uncrystal- 

 lizable ephemeral compound, being decomposed, even at a gentle heat, into 

 phosphorous acid and methyl alcohol ; it cannot possibly be mistaken for the 

 extremely stable derivative of methylphosphine, which may even be distilled 

 without undergoing any decomposition. 



Bimethylphosphinic Acid.— By this name I designate an acid which is 

 produced by the action of nitric acid on the secondary methyl base. In 

 preparing this body it is convenient to start from the chlorhydrate of dime- 

 thylphosphine. A solution of this salt is readily obtained when the crude 

 product of the action of phosphonium iodide on methyl iodide, after the ex- 

 pulsion of methylphosphine by water, is distilled with alkali, the dime- 

 thylphosphine thus disengaged being passed into hydrochloric acid. If this 

 solution be mixed with fuming nitric acid, a powerful reaction ensues, causing 

 the liquid to boil, and fumes of nitrous acid copiously to be evolved. In 

 order to free the strongly acid solution from nitric acid, it is repeatedly 

 evaporated with hydrochloric acid, and then heated for some time on the 

 water-bath to expel as far as possible also this latter acid. To get rid of 

 the last traces of hydrochloric acid, the liquid is saturated with silver oxide 

 and the solution, filtered from the silver chloride, precipitated by sulphu- 

 retted hydrogen. The solution again evaporated on the water-bath gra- 

 dually solidifies to a \yhite paraffine-like mass of crystals, which, in contact 

 with the air, are apt to become slightly brown ; they are very soluble in 



