MagcuH 15, 1912] 
between each adjacent pair of curved surfaces, a 
rolling contact which sweeps out the air ahead of 
it. The pump above mentioned has an inner 
diameter of 13 em., a depth of 4 cm., and consists 
of three rings which pump in series; the speed of 
rotation of the shaft was 800 r. per minute; 
2 H.P. suffices to operate it. 
The effectiveness of this form of pump appears 
to be due to two things: (1) A very slight travel 
of the metal parts produces a relatively rapid 
motion of the crescent-shaped spaces between the 
rings on the two plates; (2) the contacts, since 
they occur between curved surfaces of nearly the 
same radius, are relatively long; hence the vis- 
cosity of the air is sufficient to prevent appre- 
ciable leakage backwards. 
This pump may also be operated as a blower, or, 
with slight modifications, can be used as a water 
motor; indeed, since the rings may be made inde- 
pendent of one another, one can drive the pump by 
supplying water to one ring and ebtain vacuum or 
blast from the other rings. 
SECTION OF INDIA RUBBER CHEMISTRY 
D, A. Cutler, chairman 
F. J. Maywald, secretary 
W. A. Ducca: Testing Methods of Rubber Con- 
tents in Raw and Vulcanized Rubber. 
The paper deals with modern methods of rubber 
analysis by nitrosate and tetrabromide methods. 
Mostly a historical review of the work done along 
these lines. In accordance with his own experi- 
ences the author concludes that the nitrosate 
method is not suitable for the determination of 
tubber in either raw or vuleanized samples, but 
yields apparently satisfactory results for sulfur of 
vulcanization. Budde’s tetrabromide method gives 
a fair idea of the percentage of actual rubber in 
samples of raw material, but is not applicable for 
vulcanized goods. Huebner’s method, bromination 
under water, based on the Weber-Ditmar theory of 
vulcanization, is very unreliable in its present form. 
Until now only a way has been opened towards the 
development of methods to determine rubber 
directly. 
S. P. THACHER: On Mineral Compounds Used in 
Rubber. 
Victor Hanzuik: A Few Notes on Rubber Goods 
Used in Beet Sugar Factories. 
FRANCIS R. PEasopy: The Treatment of Crude 
Rubbers. 
Davi Buoom: Does the Acidity of Crude Rubber 
Resin Indicate Its Botanical Origin? 
SCIENCE 
435 
Rubber resins obtained by extraction with ace- 
tone, carefully dried and redissolved in warm alco- 
hol, were titrated with standard alkali. The acidity 
of the resin (expressed as the number of cubic 
centimeters of alkali used) is referred to a stand- 
ard quantity of the resin (one hundred milligrams) 
and this ratio is called the ‘‘acidity number.’’ 
In the course of the analyses of about one hun- 
dred and fifty varied samples of washed and un- 
washed crude rubbers, the acidity numbers of the 
resins seem to be a constant for all rubbers of the 
same class, regardless of their age or mechanical 
treatment. 
CHARLES Fox: Apocynum Rubber. 
CHARLES KNIGHT (chairman): Report of Commit- 
tee on Rubber Analysis. 
CHARLES L. PARSONS, 
Secretary 
SOCIETIES AND ACADEMIES 
THE CHICAGO SECTION OF THE AMERICAN MATHE- 
MATICAL SOCIETY 
THE twenty-ninth regular meeting of the Chi- 
cago Section of the American Mathematical So- 
ciety was held at the University of Chicago on 
Friday and Saturday, December 29-30, 1911, ex- 
tending through three half-day sessions. The total 
attendance was fifty-seven, including forty-three 
members of the society. 
Professor L. E. Dickson, chairman of the sec- 
tion, presided at the opening session on Friday 
Professor E. B. Van Vleck presided at 
the session on Friday afternoon while Professor 
Dickson was delivering his address on the ‘‘ His- 
tory of the representation of numbers as the sum 
of squares,’’ and Professor HE. J. Townsend pre- 
sided at the session on Saturday morning. 
At the business meeting on Saturday morning 
the following officers of the section for the year 
1912 were elected: Professor D. R. Curtiss, chair- 
man; H. E. Slaught, secretary, and A. L. Under- 
hill, third member of the program committee. 
On Friday noon the members lunched together 
at the Quadrangle Club, and in the evening they 
dined together at the same place and spent one of 
the most enjoyable social occasions in the history 
of the section. 
The following papers were read at this meeting: 
Professor Arnold Emch: ‘‘Involutoric circular 
transformations as a particular case of the Stein- 
erian transformation and their invariant net of 
cubies.’’” 
morning. 
