116 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
sodium hydrate were required for neutralisation. The process, 
as a routine one, might be improved by using a bulb-burette, 
the stem being graduated in 20ths of a c.c., and 5th-normal 
acid and alkali. The precise end-point to be taken ought to be 
investigated and this and the indicator standardised in some 
way. As a very general rule, however, the error of analysis 
did not exceed + 0°05% of N. (which corresponds, however, 
to + 03% of “ proteid ”’). 
Remarks on the Nitrogen Analyses. 
The estimation of NV in these products may be a matter 
of much importance, and some considerable attention was 
directed to methods. 
It is to be noted, first of all, that the order in which the © 
operations described above are carried out is of significance. 
It will be seen that the sum of the percentages of water, CCl,- 
extract, “ proteid ”’ and ash seldom add up to approximately 
100%, and (especially in the cases of some of the hermetically- 
sealed products) the deviations from 100% are much greater 
than can be reasonably attributed to experimental error. 
Now, the tissue may be dried and extracted and the residue 
then examined for N ; this was the routine usually followed. 
But the unextracted tissue might be examined directly for NV 
(in which case the digestion is more difficult, and the clear 
solution must be diluted and filtered off from the small quantity 
of fatty acids usually left, so as to avoid the formation of soaps 
in the ammonia distillation). Rather different results are 
obtained in such contrasted results. Thus :— 
% of N x 6°25 % of N x 6°25 
in the unextracted in the extracted 
substance substance 
Herrings, in tomato sauce, matured ; 
since 1914... ae 20°3 19°0 
Herrings, in mustard sauce, matured 
since 1908 . 24:0 22°6 
(Percentages calculated on the wet weights of substance). 
Salted Sprats . a ne 59°2 56°1 
Devonshire brine- frozen Sprats see 52°7 45'3 
French (Rodel) Pilchards 59°8 61:0 
French (Rodel) Pilchards (dried material 
kept 6 months) 8:7 
(Percentages calculated on the dry weights of substance). 
