Convenience in

PH

Measurements

The Type K Potentiometer Outfit shown in the accompanying illustration has come into very general use for the measurement of hydrogen ion concentrations.

Ample sensitivity and accuracy are retained under a great variety of experimental conditions, at no sacrifice of convenience. No painstaking adjustment of parts is required.

In our Catalogue S75 are described and illustrated various outfits for measurement of hydrogen ion concentrations, with various degrees of accuracy, from the potential divider method using a voltmeter (Hildebrand) to the Type K Precision Potentiometer Outfit with a highly sensitive galvanometer. Much information that may be valuable to you-thirty pages of it is also included in this new publication. Catalogue S75 will be sent you if, in writing, you will mention your position and particular interests, so that we may also send you those of our future publications which may be useful to you.

4901 STENTON AVENUE

PHILADELPHIA, PA.

Boroflux Makes Mechanically Sound Copper Castings of High Electrical Conductivity a Reality

Boroflux is a product of the General Electric Company's Research Laboratory.

The addition of Boroflux to the melting mixture produces mechanically sound, pure copper castings of the highest electrical conductivity.

Conductivity of 95% is obtainable under very favorable conditions. It is comparatively easy to obtain 90% and in a good commercial foundry 85% can be made, uniformly.

Copper deoxidized by Boroflux may be cast in green dry sand or metal moulds as readily as is brass. Boron will not combine or alloy with copper and but one-half pound per hundred pounds of copper is required.

In these times when exceptional results are vital every means for improvement is worthy of consideration. Write the G-E Office at Schenectady, N. Y.

35B-21

General Electric

General Office
Schenectady, N.Y

Company

Sales Offices in
all large cities

DIFCO

Dehydrated Culture Media

ACCURACY is the goal of all work in bacteriology, as well as in
chemistry. It is better served when all bacteriologists work
with uniform culture media, standardized to a high degree of
uniformity, as in the use of "Difco" Culture Media, Dehy-
drated. Uniformity of cultural factors is assured, either for
the same worker at different times, or for different workers
at the same time.

SPEED is greatly desired in bacteriological procedure and no ad-
vance in this respect has been made for many years that com-
pares with the use of "Difco" Culture Media, Dehydrated.
The saving in time, as contrasted with the old methods, is easily
demonstrated, and the difference is incredible.

CONVENIENCE becomes a prime consideration when accuracy

and speed are at stake. The convenience of "Difco" Culture
Media, Dehydrated, can be appreciated only by actual trial.
Think of having a dozen different formulas in convenient
packages on your shelves, needing only one weighing and the
addition of water to obtain a medium ready to sterilize.

ECONOMY is a consideration when quality has been satisfied.
The use of "Difco" Culture Media, Dehydrated, assures
economy, not only thru the factors of Accuracy, Speed, and
Convenience, but by actual comparison of costs, based on
materials, labor and time.

More than a dozen standard formulae, all carried in stock by
the principal dealers in scientific supplies. Descriptive bulle-
tins upon request.

Your inquiries are solicited

DIGESTIVE FERMENTS COMPANY

DETROIT, MICHIGAN, U. S. A.

THE CENCO FRICTION DRIVE

UNIVERSAL MOTOR STIRRER

Has Attained Unusual Popularity Because of Many New and Unusual Features

Complete Description and Price will be found in Bulletin 855

CENTRAL SCIENTIFIC COMPANY

460 East Ohio Street

CHICAGO, U. S. A.

Immediate Delivery. Write for our booklet on Blood Chemistry

C. M. SORENSEN CO., Inc., Dept. K

GENERAL DISTRIBUTORS

177 East 87th Street

NEW YORK