Cary

---

INSTRUMENTATION

Cary

instrument abstracts

Applied Physics Corporation/Pasadena/California

For Ultraviolet-Visible S p e c t r o p h o t o m e t r y

The Cary Model 11 provides performance comparable to the finest; cost comparable to the cheapest. Figure 3. partment

Details o f weighing com­

tively and providing a feed-back loop to supply the load-balancing current. Ob­ viously, this system could provide a continuous or recorded record of changes in weight as a function of time or en­ vironment. New Electromagnetic Weighing Balance

Considering the purchase of a recording spectrophotometer? The f o l l o w i n g comments m a y help y o u get much m o r e f o r your m o n e y .

Most spectrophotometer users regard the Cary Model 14, with its 1860 Â to 2.6 m u wavelength as the finest r e c o r d i n g s p e c t r o p h o t o m e t e r available. We have been surprised to discover t h a t quite a few p e o p l e d o n o t r e a l i z e t h a t t h e M o d e l 14 has a c o m p a n i o n i n s t r u m e n t — t h e C a r y M o d e l 1 1 — w h i c h gives t h e same high quality of the Model 14 at a cost comparable to the lowestprice recording spectrophotometer. T h e difference between the Model 11 and the Model 14 is in wavelength range. Of course, where the wider wavelength range is required, the Model 14 is t h e finest i n s t r u m e n t available. However, for applications in the ultraviolet and visible ranges

(2100 Â to 8000 Â) the Cary Model 11 provides the same high degree of accuracy, ruggedness, and dependability as the Model 14, as well as its convenience and flexibility, including linear wavelength recording, speed of scanning, accessories, etc. Important performance data on the Cary Model 11 are outlined below. Stray Light: Less than 0.0001% over most of the range. Scanning Speeds) 1.0 A. per second (ultraviolet region) to 125 A per second ( visible region ). Resolution: 1.0 A or better throughout most of the range. Wavelength Accuracy: Better than 5.0 A in the Ultraviolet region and better than 10.0 A in the visible region. Reproducibility: Better dian 0.5 A in the ultraviolet and 3.0 A in the visible region. Photometric Reproducibility: Reproducibility better than .004 in absorbance can be achieved with the Model 11.

20,000 HOUftS OF SERVICE WITHOUT MAJOR REPAIRS

The first Cary Model 11 was produced in service other than routine maintenance. 1Θ47, and since then nearly every lead­ This instrument has now begun a second stint of reliable service which will ing analytical laboratory in the United undoubtedly run into additional thou­ States—and many abroad—has acquired one or more Model l l ' s . The perform­ sands of hours. ance, flexibility and reliability of the FREE BULLETIN Model 11 have been proved in all kinds If your spectrophotometer applications of research and control applications. are in the visible or ultraviolet range, One of the first instruments to be man­ investigate the many advantages of the ufactured—Serial No. 2—was recently Cary Model 11. For complete informa­ overhauled at the factory after having tion write to Applied Physics Corpora­ tion, 362 West Colorado Street, Pasadena been in use twelve hours per day for 1, California, for Bulletin AC-24. over six years without requiring any For furtter information, circle number 50 A en Readers' Service Card, page 77 A 50 A

·

ANALYTICAL CHEMISTRY

An instrument employing some of these principles has been developed by the Cahn Instrument Co., 7712 Danvers St., Downey, Calif. I t is manually operated, although a recording version is contemplated. A general view of the Electrobalance is shown in Figure 1. I t is rugged, unaffected by shock, vibra­ tion, or temperature change and is port­ able. The dimensions are 10 X 10 X 7 inches and it weighs less than 12 pounds. The weighing compartment is in the upper right and the only essential con­ nection between it and the rest of the instrument is electrical. The beam, stirrup, and pan are made extremely light and these protect the jewel bear­ ings in the electromagnetic torque ele­ ment from severe acceleration forces. The circuit has been designed for speed and convenience as well as ac­ curacy. In use, the pan, calibrating mass, and sample weights are succes­ sively balanced by controlling current through the precision torque motor. The zero control "remembers" the cur­ rent for zero weight, and the calibrate control "remembers" the resistance needed to make the dial read directly in micrograms. I n making a weighing, the beam is balanced with the balance control. The galvanometer (upper left) is brought to null position with the mass dial, from which the mass is then read directly. These operations require 20 to 30 seconds. A schematic of the Electrobalance is shown in Figure 2. The pointer scale, behind which the pointer moves, is illuminated from the rear. Weight ranges are selected by means of a panel control. A larger view of the weighing compartment is shown in Figure 3.