VOLUME
23, NO. 11, N O V E M B E R
1951
17 A
r u g g e d and accurate!
the analyst's eolumn
T
HE p r o g r a m of meetings for 1951-52 of t h e Society of Public Analysts a n d O t h e r Analytical Chemists h a s been brought t o o u r a t t e n t i o n . T h i s British society h a s local sections a n d subject groups. Besides t h e m a i n L o n d o n Section, t h e r e a r e a N o r t h of E n g l a n d a n d a Scottish Section. T h e groups are three i n n u m b e r — M i e r o c h e m i s t r y , Physical Methods, a n d Biological M e t h o d s . T h e registered office of t h e society is 7 - 8 Idol L a n e , L o n d o n , E . C . 3 . At a regular meeting, held in London on October 3, t h e following papers were presented : A Critical Investigation of the Use of the Silver Reductor in t h e Micro-Volumetric Determination of Iron, Especially in Silicate Rocks. CHRISTINA AND R O B E R T A. CHALMERS.
Photoelectric Colorimeter
C. M I L L E R
Hydrogen peroxide is produced, even in small reductors, if air-free hydrochloricacid is n o t used, and this prevents com plete reduction of ferric aalta. T h e use of acid saturated with carbon dioxide reduces the error t o negligible proportions. Unstable end points obtained in t h e titration of ferrous iron, subsequent t o fusions with potassium bisulfate in plati num crucibles, are most probably caused by the presence of platinum(II), which reacts very slowly with eerie sulfate. I n general, t h e error in t h e determination of iron is insignificant if, near the anticipated t>nd point, titration is not delayed and t h e first color change of the indicator is noted. The use of gold crucibles eliminates all uncertainty. Results were shown for t h e determination of 0.03- t o 0.6-mg. amounts of iron, alone and in a number of silicate rocks.
for colorimetric absorption analysis in products control
-ROUY
Industrial Model For details, write Depf. AC. E . L E I T Z , I n c . , 304 Hudson Street, New York 13, Ν. Υ. LEITZ
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A Technique to Improve the Efficiency of Desiccators.
J. KING.
T h e inefficiency of t h e usual type of desiccator h a s been noted b y several workers. After a study of t h e usual methods, the author has greatly increased the efficiency of the desiccator b y a simple modification—namely, t h e placing of a cylinder of perforated zinc in t h e upper compartment of a Scheibler desiccator and rilling the annular space and t h e base with desiccant. T h e most suitable desiccant is calcium carbide in lumps about half an inch in diameter. Figures showing t h e absorption of moisture b y flour previously dried a t 110° C , samples of which were placed in t h e modified calcium carbide desic cator and in t h e usual calcium chloride desiccator of Scheibler pattern, show t h e improvement in efficiency. Controlled Potential Electrolysis in t h e Analysis of Copper-Base Alloys. G. W. C. M I L N E R AND R . N . W H I T T E M .
Details were given of a simple electronic instrument t h a t has been built for auto matically controlling t h e potential of the cathode with respect to a standard refer ence electrode in electrogravimetric deter mination of metals. With this instrument κ scheme for determining the majority of (Continuel/ on page 19 A)
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