V O L U M E 22, NO. 1, J A N U A R Y 1 9 5 0 37A

NEW: THE INFLUX ( Improved D r o p p i n g Funnel)

made by

ECK & KREBS, INC. 2709—40th Avenue

Long Island City 1, Ν. Υ.

makers of

HIGH VACUUM S T O P C O C K S DIFFUSION and TOEPLER P U M P S McLEOD GAUGES also SPECIAL APPARATUS

U.S. Pat. No. 2,426,556

Hermetically sealed amplifier for permanently reliable service even in humid atmospheres. Minimum grid current for accurate measurement of non-aqueous samples including oils.

Write for 7-page descriptive Bulletin #110 to

P H O T O V O L T CORP. 95 Mad ison A v e . Also: Photoelectric Colorimeters and Fluorescence Meters,

Reflection Meters, Densitometers, Electronic Photometers New York 16, Ν .Υ .

yCdct* Duo-Seal Vacuum Pumps

H I G H V A C U U M - 1 / 1 0 Micron Guaranteed FREE AIR CAPACITY - 2 1 Liters Per Minute

• Fast Pumping at al l

Pressures

• Noiseless Opera t i on

• Dependab le Results

Pat. No. 2,337,84»

DURABLE

EFFICIENT

ECONOMICAL

No. 1400-B DUO-SEAL VACUUM PUMP

(Motor Driven)

*95.°2 Complete with Motor

IMMEDIATE SHIPMENT

W. M. WELCH SCIENTIFIC C O M P A N Y 1515 SEDGWICK STREET, DEPT. A CHICAGO 10. ILLINOIS. U.S.A.

PHOTOVOLT Line-Operated Electronic

pH METER A truly universal instrument

• for accurate p H readings in laboratory and factory use • for operation with any types and designs of electrodes • for p H tests, titration, and oxidation-reduction potentials • with 7" scale from p H 0 to 14, without reversal or switching • fully stabilized, for A C lines 90 -275 volts 5 0 - 6 0 cycles • for continuous operation, also adaptable for recording • available with protective wooden housing for portability • furnished with shielded glass electrode, also available

with shielded compartment for unshielded micro-electrodes