New York Agricultural Experiment Station. 383 
over most of them that it requires comparatively little time. As some 
slight changes have been made in the manner of conducting the test, 
the method as applied to the examination of butter is described in 
full. 
Fifteen grams of the filtered butter fat are weighed into a beaker 
of about 500 cc. capacity, and 10 cc. of a solution of potassium 
hydrate (1 cc. = 0.5 gm. K O H), and 10 cc. of 95 per cent alcohol 
added. The beaker is placed upon a water bath and heated, the con- 
tents being occasionally stirred, until saponification is complete and 
the alcohol evaporated. About 300 cc. of water are then added and 
warmed until the soap is completely dissolved, the beaker meanwhile 
being covered to prevent the formation of a film over the surface of 
the liquid. When the solution is clear, 10 cc. more of the potassium 
hydrate solution are added, the beaker being left upon the water bath 
till the precipitate which forms is dissolved. The same results will be 
attained by adding 20 cc. of the potassium hydrate solution at once to 
the fat before saponification, but in this case the soap formed will be 
difficultly soluble and considerable more time will be required in 
making the solution. The soap solution is transferred to a 500 cc. 
flask, which is then filled to the mark with water. The solution is 
cooled to 20 C, the volume accurately adjusted to 500 cc. and its 
viscosity determined. 
When treated in this way each of the fatty acids, stearic, oleic, pal- 
mitic, etc., which enter into the composition of fats and oils, forms a 
soap, the solution of which has a definite coefficient of viscosity. More- 
over, this coefficient of viscosity is increased in a manner peculiar to 
each of these acids by the addition of alkali to the scap solutions. It 
follows that any changes in the composition of the natural fats and 
oils will be indicated, either by changes in the viscosity of the soap 
solutions or by the effect produced by the addition of definite quanti- 
ties of alkili (K O H). The soaps from fatty acids of high molecular 
weight, as stearic and oleic, have a high coefficient of viscosity, while 
those from acids of low molecular weight, as butyric and caproic, have 
low coefficients of viscosity. This is partially due to the difference in 
the neutralizing power of the acids, the soap solutions from acids of 
high molecular weight being more alkaline than the others, but this 
only accounts for a part of the difference, as even when the solutions 
are made to contain the same amount of free alkali a marked difference 
still exists. As a considerable portion of the fatty acids of butter have 
a low molecular weight, the viscosity of its soap solution is low when 
compared to that from the fats and v>ils which are used for its adultera- 
tion. For instance, the average viscosity of solutions of soaps from 
