248 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [18] 
chloride within which it is safe to work. It should be noted, however, 
that the solutions contained in all cases a small, but only a small, amount 
of free hydrochloric acid, and that only a small excess of barium chloride 
was used in the precipitation. Practically, we find the ordinary method 
as recommended by Fresenius accurate for these determinations, even 
in presence of the large amounts of sodium chloride, provided the proper 
precautions are observed. But the solution must be sufficiently dilute, 
and excess of free acid and of barium chloride should be avoided. 
Chlorine was determined by burning the substance in platinum evap- 
orating dishes, as in the determinations of phosphorus and sulphur, and 
estimating the chlorine in the fused mass with ammonium sulphocyanate 
by Volhard’s process. Dr. Long, by whom the determinations were 
made, has, at my request, made tests of the applicability of this method 
of determining chlorine in animal tissues. 
Ten parts of & mixture of equal weights of sodium carbonate and po- 
tassium nitrate were used to each part of the substance for the oxidation. 
To test the conditions in which chlorine may be lost in the burning, ex- 
periments were made with sugar and sodium chloride intimately mixed. 
Allowing for the very small amounts of chlorine in the sugar, it was 
found that when the oxidation was conducted slowly and carefully the 
whole of the chlorine was, in each of four trials, recovered ; but with 
rapid burning in four trials from 1.0 to 2.7 per cent. of the whole chlo- 
rine was lost. But while no appreciable amount of chlorine escapes in 
careful burning there is apt to be great loss of it if its determinations in 
the fused mass is attempted in the ordinary way by dissolving, precipi- 
tating with silver nitrate and weighing as silver chloride. Indeed, Dr. 
Long found that in some eases less than half as much chlorine was ob- 
tained by the gravimetric methods as by Volhard’s process. 
The method actually followed in the determinations was as follows: 
Ist. The substance was slowly fused with the mixed nitrate and car- 
bonate’so as to avoid any possible loss by spurting. 
2d. The fused mass was dissolved in quite dilute nitric acid, since by 
using a stronger acid some chlorine could easily be driven off, as was 
found by experiment. 
3d. To the solution thus obtained an excess of silver nitrate solution 
was added, and the whole boiled on the water bath for about two hours. 
This long boiling with excess of nitric acid, added after the silver 
nitrate, was necessary to expel nitrous acid coming from the reduction 
of the nitrate in the fusion. 
4th. After the boiling, the solution was allowed to become quite cold 
before titrating. 
