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STANDARDS OF SELF

INDUCTANCE

Wound on Bakelite, these standards of Inductance are very constant in form and do not change with age and use. Their time constant is higher than usually offered. The wire used is finely divided stranded wire, the individual strands of which are insulated from each other. The construction renders these units accurate, permanent and constant for all frequencies up to the tone of radio frequencies. Supplied in various values from 1 millihenry to 1 henry.

BROOKS' VARIABLE SELF AND MUTUAL INDUCTOR

constructed in ranges up to 100 millihenrys. It is astatic, has a high time constant and practically a linear scale. The coils will dissipate a very considerable amount of heat. The moving element is made of Bakelite.

Bulletin No. 10 treats of "Secondary Standards of Inductance."'
We will gladly mail you a copy.

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is an appropriate and highly convenient instrument for this purpose in laboratories of Chemistry, Biology, Bacteriology and Physics.

Catalogue S70 tells about this instrument and its accessories It awaits your request

LEEDS AND NORTHRUP COMPANY

ELECTRICAL MEASURING INSTRUMENTS

4901 STENTON AVENUE

PHILADELPHIA

"The Bock-Benedict"

colorimeter, as devised by Dr. Joseph C. Bock and Dr. Stanley R. Benedict of the Department of Chemistry, Cornell University Medical College, New York, and fully described in the August number of the Journal of Biological Chemistry, 1918, a highly accurate and inexpensive plunger type colorimeter, having fused cups, plungers and cells, which will resist acids and alkalies.

The instrument complete, ready for work, with plunger, cup for the unknown and one cell for the standard, (choice of 8 x 10 mm., or 15 x 20 mm. cell Extra plungers, each Extra cups

$40.00

1.15

1.15

Extra cells, 8x10 mm. or 15x20 mm., each 2.30

Guaranteed accurate standard solutions and reagents for the estimation of urea, uric acid, creatinine, and blood sugar, made up in the proper strengths to be used in conjunction with the Bock-Benedict, Kober, Duboscq and V. C. Meyers colorimeters are supplied by us. Ask for our list on complete outfit for chemical blood analysis.

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

177 East 87th Street

New York

JAY

Every Practicing Chemist Should Have

Patterson's German-English Dictionary for Chemists

By AUSTIN M. PATTERSON, Ph.D., Editor of Chemical Terms for Webster's
New International Dictionary

Places at your disposal, over 30,000 definitions, is up to date on radio activity, colloidal chemistry, etc., and gives information concerning many common abbreviations seldom found in the dictionaries. Also contains many useful hints in the correct translation of inorganic and organic You cannot afford to be without this book.

names.

332 pages.

5 by 7.

Flexible binding.

$2.50 net.

Quantitative Analysis

Fifth Edition, Total issue 19,000. Being Volume II of Analytical Chemistry.
By the late F. P. TREADWELL, Ph.D., Transacted by WILLIAM T. HALL,
Associate Professor of Chemistry, Massachusetts Institute of Technology.

This new edition contains a number of methods which have never been in the original German text. These have been tested in the laboratories of the Massachusetts Institute of Technology, in nearly every case.

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