SEA-FISHERIES LABORATORY. 115 
and ether. Its nature is bemg investigated and apparently it 
is some substance formed by oxidation of part of the dried 
unextracted tissue. 
The oil extracted from the sprats and whitebait was 
apparently similar to that obtained from herrings, but no 
chemical or physical examinations were made. 
As a rule, from 7 to 9 gms. of wet tissue were taken for 
the analysis. From 0-5 to about 1-5 gms. of oil were usually 
obtained—enough for a nitrogen estimation. About 1-5 to 
2 gms. of dried residue remained in the thimble. This was 
detached, ground up into a fine powder and replaced in its 
own weighing bottle. About 0-5 to 1 gm. was taken and ignited 
in a porcelain capsule for the estimation of non-volatile, 
mineral matter, and enough remained for nitrogen analyses : 
0-500 gm. beimg taken for the latter estimation. When the 
dried residue had been stored for some days it was always 
re-dried before the estimation. 
The digestion of the fat-free dry residue was carried out 
in long-necked Kjeldahl flasks, three operations, as a rule, 
proceeding simultaneously. Several grams of dried sodium 
sulphate were used to raise the temperature, and 20 c.c. of 
sulphuric acid were always used for the digestion. Copper 
sulphate was used to accelerate the process, which took from 
three-quarters to one hour as a general rule. 
The clear solutions in the Kjeldahl flasks were allowed to 
cool and were diluted. As a rule, the flasks were corked and 
the distillations were made on the day following that of the 
digestion. The distillation was made in the usual manner, 
deci-normal sulphuric acid and deci-normal sodium hydrate 
being used. Cochineal was employed as an indicator and 
gave better results than litmus or methyl-orange. Even then 
the discrimination of the best colour end-point was a source 
of some uncertainty and error. The ammonia distilled off was 
received into 75 c.c. N/10 H,SO, and about 17 to 25 ¢.c. N/10 
