ALKALI METAL ; EDWARD DIVERS. 29 



washed out with dilute nitric acid* and ammonia, weighed 3.8 

 grams, the calculated quantity being 3.95 grams. The nitrite 

 detected in the mother-liquor of the black precipitate had been 

 formed in too small a quantity to materially affect the weight 

 of the metallic silver. 



Generally, sodium hydroxide was approximately estimated, 

 after all hyponitrite had been precipitated, by titration with 

 nitric acid of the mother-liquor and the silver oxide precipi- 

 tated with the silver hyponitrite and metallic silver. The 

 amalgam used was of approximately known strength ascertained, 

 not by sampling which is impracticable, but by uniformly 

 preparing successive quantities and sacrificing one to assay by 

 dilute sulphuric acid and weighing sodium as sulphate. After 

 use in reducing nitrite, the sodium remaining in the mercury 

 was sometimes similarly determined. Nitrous oxide and nitro- 

 gen were not measured — their total nitrogen was found by dif- 

 ference, and their proportions had been sufficiently ascertained 

 by de Wilde, as I have already said — but their relative abun- 

 dance was estimated by a burning splint of wood, the reduction 

 of the nitrite being always conducted in a loosely closed flask. 

 The range of this reaction was from that of a gas utterly ex- 

 tinguishing combustion to that of one which supported it most 

 vividly ; in any uniformly conducted experiment the gases 

 evolved towards the end behaved like those at first given off. 

 To ascertain the effect upon its reduction by sodium, nega- 



*It was proved many years ago that silver is insoluble in dilute nitric acid, the pre- 

 sence of nitrous acid being necessary to make it dissolve. But the contrary has been since 

 asserted to be tnae where the silver is finely divided, as when precipitated. This error (as 

 I must regard it t(5 be) is due to precipitated silver when black or blackish containing 

 suboxide, which gives it its colour : this is resolved by acid into oxide of silver which dis- 

 solves, metallic silver remaining. 



