98 
IOWA ACADEMY OF SCIENCES. 
SPECIFIC GRAVITY. 
In making the density determinations a Sprengel’s piknome- 
ter of about lOcc capacity, with thermometer fused in, was 
employed. The thermometer in this instrument was divided 
into one- tenth degrees and fiftieths could readily be estimated. 
The density of every solution was determined at two tempera- 
tures, from which that at 25*^ was calculated by interpolation. 
All weighings are reduced to vaccuo, but no correction is 
applied for varying moisture of the air. 
VISCOSITY. 
The determinations of fluid friction were made by the method 
and with the apparatus described by Ostwald (Lehrbuch, 1891, 
B. I, p. 549). 
The observations for each solution were repeated at several 
different temperatures, above and below 20*^C. The time of 
flow at the latter temperature was then calculated by means of 
the interpolation formula ^ 3 ^ 0 = in which 
y ^Q=time of flow at 20°C. 
t°=r temperature of the observation. 
y^Q=time of flow observed at t°. 
k=constant for each solution, its value lying between 4 and 10 accord- 
ing to the concentration of the solution. 
Each value for obtained in this way represented the 
mean result of from four to fifteen independent observations, 
based upon the time of flow of amyl alcohol taken as 100 . 
To deduce from these numbers the relative viscosities, each 
must be multiplied by the density found for the same solution. 
In spite of the care taken to secure accurate results, it is 
believed that those actually obtained are only approximate, in 
consequence of the fact that all the solutions exhibited from the 
time of preparation a constantly diminishing viscosity. This 
change was more noticeable in the more concentrated solutions, 
and was not noticed until the series of observations was nearly 
complete. The cause is entirely unknown, but the most likely 
supposition is that a gradual breakdown of more complex 
molecular aggregates at first formed occurs. The phenomenon 
recalls that of “ birotation,” which has been observed in freshly 
prepared solutions of many optically active compounds. 
