THE ELECTRIC CONDUCTIVITY OP NITRIC ACID. 



389 



on finely -powdered calcium carbonate (Iceland spar and marble) either at ordinary 

 temperatures or the boiling point. Vitreous phosphorus at first melts in the acid 

 and then catches fire, while a considerable quantity of a dark-red sublimate (pro- 

 bably phosphorus suboxide P 4 0) condenses in the walls of the tube above the surface 

 of the liquid ; flowers of sulphur, as also iron pyrites, dissolve quickly and completely 

 in the gently-warmed acid. Nitration of aromatic hydrocarbons is readily effected 

 by the acid, whilst such a substance as chloral hydrate is decomposed, with complete 

 conversion of the chlorine into hydrochloric acid. 



(ii.) Determination of Density. 



For this purpose the form of Sprengel pyknometer, as modified by DITTMAR, was 

 used, and of capacity about 54 cub. centims. ; the ends of both limbs were closed by 

 caps, and on account of the high coefficient of expansion a series of bulbs were blown 

 on one limb of the U tube. 



The necessary corrections were made for reducing the observations to weighings 

 in vacuo. 



The following results were obtained : 



Density 4/4 = 1-54216 (i.) 

 - 1-54209 (ii.) 



Density 14'2/4 = 1-52236 (i.) 

 = 1-52231 (ii.) 



Density 24'2/4 = 1-50390 (i.) 

 = 1-50398 (ii.) 



Mean 



1-54212 



Mean 



1-52234 



Mean 



1-50394 



The values obtained by former observers are given for the sake of comparison. 



The results of LUNGE and NEF, as also of PERKIN, do not differ materially from 

 those obtained by us after allowance is made for the slightly higher percentage 

 strength and lower temperature, while those of KOLB are considerably higher ; the 

 method adopted by the last for the determination of acidity was, however, open to 

 considerable objection, though his preliminary, methods of purification were similar 

 to those described above. It is proposed to publish shortly an account of the 

 determination of densities and of other physical properties of the acid to confirm the 

 conclusions drawn from -the present work. 





