SPARKLESS ELECTRIC LABORATORY STIRRER
the ANALYST'S column
NON-SPARKING INDUCTION TYPE MOTOR
L.T.Hallett, Editor
A
"GEOLOGICAL
SLEEPEK"
is
the
way Daniel S. Turner, Geologi cal Consultant, C. A. Johnson Build ing, Denver, Colo., characterizes selenium. Based on letters received following publication of an article b y Turner, selenium, while a geological "sleeper," is most active indus trially. In t h e Analyst's Column for September, we referred t o Turner's statement t h a t " t h e demand for selenium is estimated a t twice t h e present supply." T u r n e r further indicated t h a t selenium is produced primarily as a by-product of t h e base metal industry because no naturally occurring reserves are known. H e also observed t h a t there are no adequate qualitative or quantitative tests for use in field work. Letters have been received from the American Smelting and Refining Co. a n d the General Chemical Division, Allied Chemical and D y e Corp., stating t h a t consumption increased rapidly in t h e recent past when selenium rectifiers were replac ing t h e copper oxide and some vacuum t u b e rectifiers. Users also stockpiled extra inventories, putting a strain on t h e supply of selenium. With this increase in use there was a price rise. Late in 1956, for exam ple, ceramic grade selenium reached a peak price of $15.50 a pound. In 1957 it h a s been quoted a t $12 a pound. T h e authors indicate t h a t there was no period when dealers lacked selenium rectifiers. This rapid growth is over a n d , with t h e marketing of silicon semi conductors, there will probably be some inroads into selenium usage in power rectifiers. Authors of these two letters state further t h a t t h e question of recover ing selenium as a by-product in copper refining and from sulfide
An Ideal General Purpose Stirrer
Reduces Explosion Hazard from Brush Contacts Watt-Type
Governor Stabilizes Speed
^=
$54.75
w No 523
• AUTOMATIC SPEED CONTROL ° • QUIET OPERATION · LONG LIFE 5230. ELECTRIC STIRRER, Sparkless. Complete with 0-foot connecting cord, line switch, and plue;. For operation on 50 or 60 cycles, 115 volts A.C. Each $54.75
S230A. ELECTRIC STIRRER, Sparkless, for 230 Volts, A.C. Consists of No. 2530 Stirrer equipped with a step-down trans former to permit operation on 230 volts 50 or 60 cycles A.C. Each S64.S0
W. M . WELCH SCIENTIFIC COMPANY DIVISION OF W. M. WELCH MANUFACTURING COMPANY
ΕSTABLISHED 1880 • 1515 SEDGWICK STREET, DEPT. A - 1 , C H I C A G O 10, ILLINOIS, U.S.A. Manufacturers of Scientific Instruments and Laboratory Apparatus
Presenting the NEW
HEVI-DUTY "G-07-PT" LABORATORY FURNACE
if if
TEMPERATURE RANGE TO 2600° A COMPLETE SELF-CONTAINED FURNACE if POSITIVE TEMPERATURE CONTROL if PROVIDES FAST UNIFORM HEATING
The Hevi-Duty G-07-PT Furnace is a complete unit ready for use. All the temperature control and indicating de vices are located in the furnace base. A tap-changing transformer equipped with two selector switches offers 48 steps of temperature control. This method allows close temperature regu lation and means savings in power and
maintenance. An indicating pyrometer and ammeter are mounted for easy observation. Easily replaceable Silicon Carbide heating elements provide a uniform heat above and below a ceramic muffle which forms the heating chamber. In side dimensions 4'/s" wide, 2^4" high, 7" deep.
SEND FOR DETAILS IN BULLETIN 957A
HEVI-DUTY LABORATORY FURNACES
ELECTRIC COMPANY ELECTRIC EXCLUSIVELY HEVI DUTY®
MILWAUKEE 1, WISCONSIN For further information, circle number 47 A on Readers' Service Card, page 83 A
VOL. 29, NO. 12, DECEMBER 1957 ·
47A
