598 BISMUTH. 



Subnitrate of bismuth, HO, NO 5 -f 3BiO, mentioned above, 

 is produced at a temperature so low as 180, and may be exposed 

 to a temperature of 500 without decomposition. At a higher 

 temperature its acid and water go off together. It is the only 

 subnitrate of bismuth ever produced, in the decomposition of 

 the neutral nitrate by heat. When crystals of the neutral ni- 

 trate are decomposed by 24 times their weight of water, they 

 give, according to M. Duflos, a hydrated subnitrate containing 

 NO 5 , 4Bi O and 3 HO. This subnitrate, which is used in phar- 

 macy and known as the magistery of bismuth, is a brilliant 

 white powder of pearly lustre, composed of microscopic crystal- 

 line grains; which is light after being dried, like magnesia alba. 

 When prepared by pouring the solution of the neutral nitrate, 

 drop by drop, into a large quantity of water, the composition 

 of the subnitrate is 3BiO + NO 5 , according to Mr. Phillips. 

 The subnitrate of bismuth is employed as a cosmetic ; it is also 

 used as an internal remedy. 



Peroxide of bismuth, Bi O 2 , was formed by Stromeyer by 

 boiling anhydrous protoxide of bismuth finely levigated, with 

 chloride of soda. It is a dark brown anhydrous powder, which 

 gives chlorine with hydrochloric acid, but is not reduced to the 

 state of protoxide by sulphurous acid. 



The alloys of bismuth are remarkable for their fusibility. The 

 Amalgam of this metal is highly liquid. An alloy of 8 parts bis- 

 muth, 5 lead and 3 tin melts at 202; another mixture of 2 bis- 

 muth, 1 lead and 1 tin at 200.7o, these mixtures are known as 

 fusible metal. Bismuth is also added to the alloy of tin and 

 lead used for casting stereotype plates. Besides increased fusi- 

 bility, bismuth communicates to this alloy the property of ex- 

 panding on becoming solid, by which it is calculated to take an 

 accurate impression. 



