262 Raymond H. Pond. 
lowance was made for deliquescence during weighing. However the 
weighing was done as rapidly as possible. The deliquescent salts 
were all obtained in the crystalline form. Error due to deliquescence 
is negligible in view of the concentrations used. The molecular 
weights were based upon the international table of atomic weights 
with oxygen as sixteen. All the solutions were made up molecular, 
so that M-32 silver.nitrate is equivalent with M-—64 of barium nitrate. 
The actual values used are as follows: 
Nitrates. Mol. weight. Nitrates. Mol. weight. 
mondidin sk se Magnesium + 6 water . . 256.536 
we sy ae Mercury (chlorid). . . . 270.g00 
Cadmium + 4 water. . 308.544. Potassium Ne re ae oe 
Cova) 6 water... 991.996 Silver 27. 0). ieee 
Copper +3 water . . 241.728 Sodium. . . . - 85.090 
Rea ee 330.980 Strontitay’ ss 5 Ss ee 
ambiNiR  og e 69.070 Zinc+6water . . . + 297-576 
The use of ethylbutyrate.— This ester is suitable because it can 
beused pure. The butyric acid arising from its saponification readily 
dissolves in water containing the alcohol which forms simulta- 
neously with the acid. Being lighter than water and only slightly 
miscible, it floats upon the surface so that the saponification products 
diffuse downward as rapidly as formed, leaving the residual butyrate 
€xposed to the action of the enzyme. As obtained under the label 
“absolute,” ethylbutyrate contains saponification products and has 
an acid reaction. A supply of pure and hence neutral butyrate was 
Prepared and kept as follows: On shaking with water several times 
in a separatory funnel the acid and the alcohol can be removed. 
Further shaking with dilute alkali to which some litmus has been 
added completes the preparation. Thus a stoppered cylinder contains 
two separate liquids. The lower one is blue if alkalin, and the upper 
one, the butyrate, is clear, and may be regarded as neutral as long as 
the lower liquid separates blue after thorough shaking. If the container 
is carefully stoppered, the spontaneous saponification is not rapid, and 
y shaking each evening one can have each morning a supply of neu- 
tral butyrate which may be withdrawn with a pipette. Sucha neutral 
butyrate will not develop an acid reaction in distilled water during an 
incubation of four hours at 40° C. 
Titration with phenolthalin, — This indicator proved very satisfac- 
tory, and was used in every case except that ofammonium. The same 
