CHEMICAL CHANGES OCCURRING IN OYSTERS. 7 
posed at the end of the week. In this lot, the values for both amino- 
acid and ammoniacal nitrogen were smaller at the end than they were 
at the beginning of the experiment. 
Of the two determinations intended to show the amount of de¬ 
composition which has occurred in oysters, it appears that deter¬ 
mination of ammoniacal nitrogen by the Folin method is worthless 
in commercial oyster work for the following reasons: 
(a) The free ammonia and ammonium salts are washed out of the 
oysters nearly as fast as they form. 
(b) The very small amount of standard acid neutralized by the am¬ 
monia makes the probable error relatively large. 
(c) 'W ith alizarin red as an indicator, the color change obtained is 
not sharp, under such conditions. 
For the last two reasons, duplicate determinations often varied 
widely, and no great reliance is to be placed upon the accuracy of 
the determinations; hence, very little weight should be attached to 
the meaning of the results obtained. Often higher ammoniacal 
nitrogen figures were obtained from fresh oysters than from others 
which had undergone decomposition. 
It is believed that the amino-acid nitrogen determination is much 
more consistent and reliable. It is more consistent in that a larger 
amount of solution is taken for titration, which lessens the probable 
error, and in that the end point is easier to locate. The principal 
objection to this determination is that the amino-acid nitrogen con¬ 
tent is not a true indication of the amount of decomposition which 
has taken place in the oysters, for the following reasons: 
(a) Amino acids, being soluble, are washed out of the oysters by 
each change of water in the same way as are the ammonia 
and its compounds. 
(b) Amino acids present a very suitable medium for bacteriological 
growth, and are, therefore, being continuously broken’down 
into some of the simpler compounds already mentioned. 
Therefore, the amount of amino acids present is never a 
measure of the total amount of decomposition, and in many 
cases is a measure of only a very small percentage of it. 
However, the results obtained on oysters undergoing wash¬ 
ing treatments are comparable, and are of great value in 
indicating the amount of soluble matter removed. 
In the study of washing oysters, the greatest reliance is to be 
placed upon the determinations for amino-acid nitrogen, total solids, 
and ash. The figures for moisture are very useful in showing the 
amount of water added to the oysters in the washing processes. 
The determinations for salinity were of little assistance, as the salt 
was removed quite completely in a comparatively brief period of 
washing. 
