24 A
ANALYTICAL
CHEMISTRY
INSTRUMENTATION
Now—anyone can make accurate determinations with a
improvement in performance of given instruments. In many cases, improved or more elaborate recorders and controllers are characterized by much smaller dead zones and high speed corrective action. This is true to the extent that further improvement in over-all per formance must be sought elsewhere in the system. Ionization
Designed to measure both
DIFFUSE REFLECTION
(whiteness,
bright
ness, color) a n d SPECULAR REFLECTION (shininess, gloss) A c a r e f u l l y constructed a n d h i g h l y versatile i n s t r u m e n t f o r fast a n d accurate d e t e r m i n a t i o n s o n solid surfaces o f e v e r y descrip t i o n , p o w d e r s , pastes a n d o p a q u e l i q u i d s . To the basic i n s t r u ment can be a t t a c h e d a n y o f a n u m b e r o f search u n i t s , each e n g i n e e r e d especially f o r one o r more specific purposes. •
Paper
•
Detergency
brightness
•
Paint gloss tests
tests
•
Line or battery models
•
12 i n t e r c h a n g e a b l e search units
tests
A
operated
variety
o f color
filters available, in cluding those for ICI Tristimulus values.
PLENTY , SLICK IN ' APPEARANCE. TOO!
MURGATROYO 2428/3 — R e f l e c t i o n M e t e r Model 610, for 110 volt, 60 cycle, A C. Current S135.00 2428/19—Same as 2428/3, but for 6 volt storage battery operation. Without battery $120.00 * · _.ΛΛΙΛΛ „ ,„ , Λ 2428/32-Same OS 2428/3, but for either 1 10 volt 60 cycle A.C. or 6 volt storage battery operotion. Without battery. $150.00
2421/12—6 volt tery
s t o r a g e bat$19.75'
2428/4 — S e a r c h unit for genuse, with green tristimulus fil,er $65.00 ,.,-,. , ., . 2428/5 —Search unit for paper brightness t e s t s , with built-in Wratten filter # 4 9 $55.00 , w ' 2428/8 — S e a r c h unit for 60* gloss tests $75.00 e r a l
Write for Full Information on These a n d Other Units
SCHAAR & COMPANY Complete Laboratorv 7 5 0 W . LEXINGTON STREET
Equipment CHICAGO 7
Flame
Detectors
A recent study on ionization flame detectors by H. F. Calcote of Princeton University [Rev. Sci. Instruments, 20, 349 (1949) ] contains more than the solution of the intended problem of measuring flame velocities in tubes. Two new methods were developed, in one of which the loading characteristics of a high frequency oscillator are utilized by causing the flame to pass through an oscillator tank coil. As analysts well know, this is analogous to Jensen and Parrack's application to conductance titrations. In a second method, two ring electrodes are placed around the exterior of a combus tion tube and a d.c. voltage is applied across them through a large series resistance. We recall earlier treatises on the physics of conducting flames by Wilson and others and intriguing aspects which even attracted the interests of Arrhenius when he was formulating his theory of electrolytic dissociation. It would seem un wise to deny that there is analytical interest in con ducting flames, and it is equally unwise to assume that the sole analytical interest resides in the radiation which they emit. Voltage Dividers
From time to time we have expressed considerable personal satisfaction in the highly informative type of advertising which some of our instrument manufac turers put out. We have long been addicted to the General Radio Experimenter, published by the General Radio Company, Cambridge, Mass. A recent issue, Vol. 23, No. 12, contains the second part of three articles on voltage dividers, wherein our former good neighbor P. K. McElroy discusses numerous design tricks whereby the manufacturer can attempt to meet the exacting requirements of his customers. The possibili ties and limitations of designing nonlinear voltage dividers (potentiometers) are discussed in interesting and informative fashion. From this treatment one clearly gains the impression that the most exacting de mands can be met by various methods of approxima tion which at all times represent a compromise between ideal characteristics and reasonable cost. McElroy's observations are worthy of careful study and con sideration and are comparable with all the information disseminated by General Radio in its catalogs, where one usually finds every possible characteristic of an instru ment clearly and unambiguously defined, including its limitations.
