SCIENCE— ADVERTISEMENTS 



Constant-Temperature Apparatus 



Dependable for Long, Continuous and Unattended Operation 

 FREAS OVEN TYPE R No. 100 



Size of oven inside, 12"xl2"xl2". 

 Temperature range, from room to 



175°C. 

 Regulation, Freas Metallic ther- 



mo-regulator. 

 Constant within one degree over 



long periods. 



Construction, heavy asbestos tran- 

 site with cast aluminum frames 

 and insulated lining. 



Operation, simply attach to lamp 

 socket. 



Furnished with Special Ther- 

 mometer, ranging to 2(iO°C. 



SLMPLICITY oi operation, ease of regulation, constancy and 

 general dependability are the reasons why FREAS Ovens have 

 been adopted by the most important laboratories of the U. S. 

 Government, the leading educational, scientific institutions and 

 the most progressive manufacturing plants in the country, 



FREAS Ovens are made in several sizes and types. They are ap- 

 proved by the National Board of Fire Underwriters. They are 

 strongly constructed and reliable to the utmost detail. They may 

 be left in operation, unattended, for months at a time if required. 



For Sale by All Dealers in Dependable Laboratory Apparatus 



Sole Patentees and Manufacturers 



The Thermo Electric Instrument Co., "fc" Newark, N. J., U. S. A. 



MAKERS ALSO OF THE THELCO LINE 



Langmuir High- Vacuum Pump 



Dr. Irving Langmuir (of the 

 General Eleotrio Co.) has de- 

 veloped an exceedingly inter- 

 esting and yaXxL&hlb high-speed 

 high-vacuum pump, and by 

 Bpeoial agreement with the 

 makers, we are acting ai Bole 

 distributors, for laboratory 

 purposes. 



With this pump pressure as 

 low as 10~' bar have been ob- 

 tained ; and there is little 

 doubt that very much lower 

 pressures oan be produced, by 

 cooling the bulb to be ex- 

 hausted, in liquid air, so as 

 to decrease the rate at which 

 gases escape from the walls. 



Some type of primary pnmp 

 must be used ; capable of de- 

 veloping a vacuum not less 

 than 0. 1-0. 15 mm.of mercury. 

 The illustration shows a Langmuir pump, connected to a two-stage primary oil pump — which is op- 

 erated by a J HP motor ; all three parts of the outfit being assembled together on one base. 



JAMES G. BIDDLE 



1211-13 ARCH STREET 

 PHILADELPHIA 



If interested, write for copy of illustrated 

 Bulletin 881, issued November, 1917 ; 

 and also copy of paper by Dr. Langmuir. 



