Nitric Salts of Lead — Deville on Oil of Turpentine. 187 



trie oxide ; this gas escapes only when the yellow salt is de- 

 composed at a higher temperature. Should this salt be mixed 

 with any of the orange-coloured salt which will presently be 

 noticed, it may, from its far greater solubility, be separated 

 from it by treating the mixture with a quantity of warm water, 

 not sufficient to dissolve the whole. The analysis consisted 

 in the direct determination of the oxide of lead, nitrogen and 

 water; the results agree with the formula N O 4 , 2 Pb O, H O. 



Berzelius adopts hypothetically that it contains 6*4 per cent, 

 water; experiment affords but 3*2. The following simple 

 equation, N O 5 , Pb O + Pb + H O = NO 4 , 2 Pb O, HO, 



gives good account of the origin of the salt. The second salt 

 is of an orange colour, and is obtained by dissolving two and 

 a half equivalents of lead in the boiling solution of one equi- 

 valent of the nitrate of lead ; on cooling, a mixture of the yel- 

 low and orange salts is obtained ; the former is removed with 

 boiling water. All the analyses of this salt give the formula 

 N2 O 8, 7P bO, 3 HO. The constitution of this salt is 



confirmed by synthesis, for when the bibasic hyponitrate is 

 boiled with oxide of lead, the orange-coloured salt is obtained. 

 Continued boiling of nitrate of lead with more than two or 

 three equivalents of lead gives Chevreul's rose-red salt, which 

 is represented by the formula N O a , 4 Pb O, H O. (Compt. 



Rend. t. xi. p. 860.) 



Deville on Oil of Turpentine. 



M. Deville calls the oil which is contained in the artificial 

 camphor Camphen, that in the fluid product Tereben. Te- 

 reben may be obtained by distilling oil of turpentine with sul- 

 phuric acid. The temperature must not exceed 200°, for then 

 colophen passes over. By repeated distillation with sulphuric 

 acid, the tereben may be obtained pure; the only proof of its 

 purity is its having lost all power of rotation. By distilling 

 the liquid camphor with lime it cannot be obtained pure. It 

 has the same boiling point and specific gravity as oil of tur- 

 pentine. Formula C 20 H 32 . Tereben combines with the hydro- 

 chloric, hydriodic and hydrobromic acids in two proportions. 

 The monohydrochlorate of tereben is C 20 H 32 + H CI ; the 

 bihydrochlorate is C 20 H 32 + H 2 CI 2 . This latter was exa- 

 mined by Soubeiran and Capitaine; it is the liquid product 

 obtained in preparing artificial camphor; it has probably no 

 power of rotation. The monohydrochlorate is obtained by 

 passing hydrochloric acid into tereben; it is liquid ; specific 

 gravity at 20° = 0*902 ; smells like camphor ; contains four 

 volumes of vapour of tereben, and two of hydrochloric acid. 



