CHEMICAL COMPOSITION OF FOOD-FISHES. 695 
this was due to chemical or physical changes in the fats, and how far to 
coloring matters extracted with them, i can not say. 
As regards the difficulty of extracting with ether, our experience 
shows that many of the vegetable fats, as those of maize, wheat, etc., 
are easily extracted, while those of animal tissues are often more diffi- 
cult to get into solution. The fats, or, more properly, the materials 
soluble in ether, are more readily extracted from oysters, clams, lean 
beef, etc., than from the flesh of the fatter fish and the fatter meats. 
In general, the greater the percentage of fat in a substance the more 
difficult the removal of the last traces. Mr. Woods remarks that u the 
flesh of eels was the hardest material to extract I have ever met.” I 
should say that even the flesh of eel could hardly be much more diffi- 
cult than the yelk of eggs, which, however, is of different composition. 
It is, I think, very important that the material to be extracted be fine, 
especially when it is hard and dry, as is often the case with partly dried 
flesh. 
After the experience which we have had in extracting with ether, I 
am persuaded that correct results are far harder to obtain than is or- 
dinarily believed. Indeed, I regard these determinations, like those of 
water, as among the more difficult ones with which we have had to do. 
ASH. 
The ash was determined by charring about 2 grammes of the partly 
dried material, extracting the charred mass with water, burning the 
residue at a high temperature, adding the solution, evaporating and 
burning at a faint red heat. The charriug and burning were conducted 
in platinum capsules over a gas flame. The crude ash thus obtained 
was practically free from coal. No determinations of carbonic acid 
were made. 
PHOSPHORUS. 
A portion of the partly dried substance, usually about 1 gramme, 
was carefully burned in a platinum crucible with some 10 grammes of a 
mixture of equal parts of sodium nitrate and carbonate, previously 
proved free from phosphoric acid. The white mass was dissolved in 
water, acidulated with nitric acid, evaporated and treated with nitric 
acid again, the operation being repeated when necessary to remove 
chlorine, and the phosphoric acid then estimated with ammonium 
molybdate solution. 
A number of experiments were made to test the accuracy of the de- 
terminations in the presence of such large quantities of sodium nitrate, 
etc., as are necessarily used. They were carried out by Mr. G. P. Mer- 
rill, then assistant in this laboratory and now curator in the U. S. 
National Museum. It will suffice here to give the outcome, which was 
briefly this : 
At the temperature of the trials, which was in each case not far from 
