EDITOR'S COLUMN fuges with speeds of 15,000 to 20,000 revolutions per minute and analyt ical ultracentrifuges which operate at 100,000 r.p.m. This work dates back to 1927 when studies were made of virus particle sedimenta tions using an air-driven centrifuge. To study molecular weights of pro teins, a 60,000 r.p.m. centrifuge with a variation of only 0.17c "'as devel oped. Another instrument which is now a commercial development is the "ellipsometer" which measures film thicknesses only a few molecules thick. This does not use t h e inter ference method b u t is based on t h e fact t h a t a thin film on a reflecting surface changes polarization of light. The amount depends on film thickness. With this device thick nesses within 0.2 angstrom unit can be determined. In using partition chromatogra phy, particularly starch column chromatography, introduced in 1944, for studies of amino acids and peptides, t h e need for an automatic fraction collector arose. T o meet this need they developed a circular rack collector which could collect 320 fractions automatically over a period of several days. Another development was t h e Porter-Blum microtome to cut thin sections for electron microscopy. This device can be used b y rela tively unskilled personnel. T h e system to advance the knife a few millionths of an inch does not de pend on thermal expansion b u t on an automatic mechanical device. The shop h a s been working for some time on a completely robotized and wholly reliable counter cur rent distribution a p p a r a t u s which could work unattended for several days. Related to this is an instru ment for in vitro culturing of cer tain parasites which require periodic and carefully controlled exchanges of the media on which they are grown. Fresh culture medium is automatically withdrawn from a refrigerated source, automatically warmed, and introduced into flasks. This device replaces and removes automatically exhausted medium.
detect and continually r e c o r d . . .
^
CHLORIDE concentration down to 0 . 0 0 5 ppm t?
«Γί7ϊ5%·»
with
the
T E C H N I C O N ®
Auto Analyzer® Automatically analyzes or monitors chloride content of sample stream A field-proven system . . . over 2000 A u t o A n a l y z e r s are now auto mating routine wet-chemistry analyses in plants a n d laboratories throughout t h e free world . . . analyzing u p to 60 repetitive samples p e r hour a n d monitoring on-stream continuously. ^ Detects other trace elements too, e.g.; platinum, silica, tetracycline, glucose, CO·, fluoride, ethanol, etc. A total of 75 fully-automated determinations now possible, more ore coming. Send for your free abstract method kit and brochure AKE today
TECHNICON CONTROLS, INC. RESEARCH
PARK
•
C H A U Ν C Ε Υ , Ν. Υ.
Circle No. 17G on Readers' Service Card
new concepts in scientific glassware Delmar introduces
MITE-O-WARE GREASE FREE MICRO-GLASS LAB WARE • • • • •
New unique joints are leakproof O-Rings made of Viton Eliminates contamination Fast easy assembly . . . no joints to grease Viton O-Rings hold pressures as low as 10~6, for temperatures from —40° F to + 5 0 0 ° F. • New design for O-Ring needle valve stop cocks
Delmar
SCIENTIFIC LABORATORIES 317 MADISON ST., MAYWOOD, ILL
1
Write for new Mite-O-Ware , catalog A61M on MicroGlass lab ware and Catalog A60D for High Vacuum , glass ware equipment.
MirÉOGiissiinvARf
DELMAR
A SUBSIDIARY OF COLEMAN INSTRUMENTS, INC. Circle No. 46 on Readers' Service Card VOL. 33, NO. 12, NOVEMBER 1961
•
85 A
