298 MESSRS. THORPE AND MORTON ON THE 



ammonia in solution was then estimated by Nessler^s 

 method. One cubic centimetre of the solution of am- 

 monium sulphate employed in the comparison was equiva- 

 lent to 0*00010 of nitrogen. The amount of this solution 

 required to give a tint equal to that afforded by 50 cubic 

 centimetres of the distillate was (i) 6*2^ (2) 6-9^ (3) 6'2 ; 

 mean^ 6*4. Hence the ammonia in 1000 grms of water 

 = 0*000108. 



XI. Estimation of the Nitric Acid. 



The liquid remaining in the retort was carefully decanted, 

 when clear, from the precipitate formed on adding the 

 caustic soda solution; this precipitate was repeatedly 

 washed, and the washings added to the main bulk of the 

 solution. The entire quantity of the solution was then 

 concentrated until about 20 cub. cent, only of liquid re- 

 mained ; this was filtered into a small flask ; a large excess 

 of pure caustic soda was then added, and the solution was 

 boiled for about an hour, in order to remove completely 

 any traces of ammonia which might have been absorbed 

 from the air of the laboratory. When cold, two compound 

 helices of zinc and iron were thrown into the solution, 

 which was further treated according to the method of 

 Vernon Harcourt. The ammonia contained in the distil- 

 late, derived from the action of the nascent hydrogen on 

 the nitrate in solution, was estimated by Nessler^s method. 

 The weight of the distillate was 96*3 grms. One cubic cen- 

 timetre of the ammoniacal solution used for comparison was 

 equivalent to o*oooii2 NO3H. The amount of this solu- 

 tion required to afford a tint equal to that caused by 

 25 cub. cents, of the distillate was (i) 19*0, (2) 17*8, (3) 

 20*2; mean, 19*0 cub. cent. Hence the amount of nitric 

 acid contained in 1000 grms. of sea-water is 0*001563 

 grm. 



The ammonia and nitric acid contained in sea- water are 



