V O L U M E 2 6 , NO. 12, D E C E M B E R 1 9 5 4
2003 by t'wo pins, from which it could b&slipped for easy removal. -4 preliminary performance check with the mounting positioned by dimensions proved so satisfactory t h a t no provisions were made for movement of the platform. The lens system was focused by adjusting the distance between the lenses for maximum t ~ a n s mittance and the holders vere locked in position by tightening the 4-40 screws in the slot. As shown in the sketch of Anderson and s efficiently with the plane Miller (Z), the lens system ~ o r k most sides of t h e plano-convex lenses facing each other.
Beam-Condensing System for Beckman IR-2 Infrared Spectrophotometer T. Y. Toribara, Division of Pharmacology, Deportment of Radiation Biology, School of Medicine and Dentistry, University of Rochester, Rochester, N. Y. HE beam-condensing system designed by Anderson and 11iller r(0has ) been successfully installed in the Beckman IR-2 spectrophotometer, in a new section of transparent plastic which was inserted between the light source compartment and the rest of the instrument. T h e standard Beckman cell compartment may be left in place or removed. Because the beam of light passing through this part of the instrument is collimated, the light source compartment may be separated for a considerable distance without loss in sensitivity. r
Using a set of the early uncoated experimental lenses of Eastman Kodak, the transmittance was 45% a t 2 microns, increasing with wave length t o 73% at 10 microns, and continuing a t that value to 15 microns. The lenses now available from Eastman Kodak are much more transparerit ( 1 )and should give even better transmittance. When not in use, the lenses were covered to exclude light; no noticeable darkening occurred in 9 months. Thus, the Beckman IR-2 spectrophotometer may be converted easily for handling micro samples in pressed potassium bromide pellets. If the liquid cell compartment i3 left in place, this conversion is made with no reduction of existing functions. If the liquid cell compartment is removed, an opening should be provided a t the bottom of the back side of the lens compartment for the introduction of dry nitrogcw.
The lens compartment was built of 3,/a-inchmethacrylate polymer according to dimensions shown in Figure 1. The mounting for the lens system was made of brass with a design similar t o t h a t of A4ndersonand Woodall ( 3 ) and is shown in Figure 2 in views from the top and end. T h e guides for the lens holders were made by assembling strips of 1/8-inch flat brass stock. T h e plastic lens holders have been described ( 2 ) . The platform for the mount>ingwas made of '/?-inch methacrylate polymer with a brass table top. The lens syst'eni was centered in the beam by measurement from the center lines of the bolt holes. T h e mounting a a s kept in position on the platform
LITEH (I'CRE CITED
(1) Anderson, D. H., personal c o m m u n i c a t i o n . (2) Anderson, D. H., and Miller, 0. E., J . Opt. SOC.Arne,. 43, 7 7
..
(1953).
(3) Anderson, D. I I . , and Woodall, N. B., AXAL.C m s r . , 25, l 9 O G (1953). on work performed under contract with t h e United Atomic Energy Commission at t h e L-niyersity of Rochester Atomic Energy Project, Rochester, N . Y .
Ba0ED
-l b
Improved Stainless Steel Needle Valve A. R. Glasgow, Jr., and G. S. Ross, Sr. National Bureau of Standards, Washington, D. C. EEDLE
///
and vacuum systems. This type of valve with a brass body and steel stem was designed and used as early as 1927 by H. F. Stimson (unpublished work) a t the Kational Bureau of Standarch. The usual construction of noncorrosive valves, in which both the stem and body are made of stainless steel of the same hardness, has the disadvantage that in use the stem becomes scored on the needle cone by the seat and on the shaft by the steel bushing located below the packing. An improved stainless steel needle valve which eliminates these disadvantages by use of steels of two different hardnesses has now been constructed.
,' hi
-
#I
tk i
-
76.-
-
Figure 1.
4 ;/,
Isometric Drawing of Lens Compartment Showing Lens System in Position
Lens system centered 2 ' g / 3 9 inches from center line of left holes and 2 1 5 / a 2 inches from centei !me of top holes
7
6-32 TAP ONLY
SLOT FOR
4-40
-97
A;
j,+
BOTTOM PLATE
:",",',"~,'d;*," \
mw
POSITION P I N HOLE
$44
F L A T BRASS STOCK
SECTION A - A Figure 2.
valves of the Stimson type similar to that shoivn in
N Figure 1 have long been in use in thme laboratories for chemical and physical processes conducted in both high-pressure
Lens Holder and 3Iounting
The valve body is an 18-8 stainless steel and the valve stem a 440-C high-carbo11 stainless steel which, after being machined approxiinately to size, can be hardened by heat treatment, ground to the final dimensions, and highly polished. The relative difference in hardncsh I)etween t h e valve stem aiid body was found to I)e about 50 units 011 the Rockwell C scale. T h e identification nuin1)ers of the stainless Pteela refer to those uscd 1))- the . h e r i c a n Iron and Steel Institute. If the valve body is to be \velticd to a stainless steel h m i ) or container, t h c :304 or :308 \ w i e t y of the 18-8 stainless steel should be wed. T h e valve stems, including the thrc:iil~dportions, were first machined approximately to size and shape hefore being hardened by heat treatmerit. In the untreated condition the)- had a hardness of 20 on the Rockwell C wale or 97 on the 1loc.kirell B wale and were readily machincd. The sterns were then heat-treated
