244 Dr. H. Chick. The Process of Nitrification [Apr. I, 



water, it was found that when this coke is packed into a space, the volume of 



the interspaces between the pieces is oo per cent. ; 

 the volume of the pores inside the pieces (amount 

 of water retained on draining) is 20 per cent. ; 

 and the volume of solid coke is 45 per cent, of 

 the whole space. The three filters were fixed to 

 the wall, near together, and all treated in exactly 

 the same way, i.e., as continuous filters. Each 

 received 4 litres of liquid daily, and the sewage 

 employed was the liquid manure ("Jauche") 

 from a neighbouring cowshed ; this proved a 

 very suitable material, after a rough filtration 

 through glass wool, and dilution to 1 in 20 with 

 tap- water. 



This liquid was contained in a 10-litre reservoir 

 bottle of the Mariotte type, from which it 

 dropped regularly into a small vessel containing 

 a siphon arranged to empty when 100 c.e. had 

 collected (A, fig. 1) into a sprinkler (13. fig. 1), 

 the object of which was to distribute the liquid 

 as evenly as possible over the surface of the 

 filter. 



The methods of analysis employed in following 

 the course of the oxidation of nitrogen were 

 those usually adopted in such work,* but the 

 following details may be given : — 



In the estimation of free and saline ammonia, 1 to 

 10 c.c. of the liquid was taken and diluted in a retort 

 with about 500 c.c. NH 3 -free water, and distilled, it 

 being found unnecessary to add any alkali. t Three 

 successive portions of 50 c.c. were distilled off and the 

 ammonia they contained estimated by means of Nessler's 

 reagent. Albuminoid ammonia was afterwards estimated 

 by adding to the same retort a definite amount of 

 " alkaline permanganate solution," distilling as long as 

 ammonia came over in the distillate, and estimating 

 these amounts in the same way. 



O.eidiscd nitrogen in the filtrates was detected by 

 means of the reaction with diphenylamine sulphuric acid. 

 Nitrites were distinguished by reactions with acidified 



Fig. 1 — Diagram of the "Con- 

 tinuous" Filter, of medium 

 height, showing construction. 

 The contour of the filter is 

 l'epresented as interrupted at 

 K, to show the arrangement 

 of the thermometer and the 

 collecting funnel. 



* Cf. ' Report of Royal Commission on Sewage Disposal,' vol. 4, part 5. 

 t ' Sew. Com. Report,' vol. 4, part 5, appendices 3 and 4. 



