•y/,. Welch CATHETOMETER
THE ANALYST'S COLUMN
Rapid L e v e l i n g — F i n e A d j u s t m e n t Graduations Engine D i v i d e d for U n i f o r m i t y and A c c u r a c y
L.T. HALLETT, Science Editor
Please, allow an old microanalyst to add a few remarks to the article "Ele mentary Analysis of the Future," which ANALYTICAL
CHEMISTRY,
Vol. 27, page 477. The article expresses a widely spread opinion that elementary analysis is mainly a technical and a measuring problem: Physics and physical chemis try have provided for a great number of fast, accurate, and sensitive measur ing methods. Why not use them? Let me say it: Elementary analysis is not a measuring problem nor is it a problem of designing automatic devices. You must have something to measure first. The elementary analyst is expected to present good results for a wide variety of compounds with many different constitu ents and constitutions. His problems are chemical problems—problems to ob tain quantitative combustion, quantita tive separations, to avoid contamina tions from the reagents and from the wall materials of the combustion vessels, and to avoid side reactions and inter ferences from other constituents of the samples. Once a good combustion pro cedure has been designed, the measure ment is no problem. Even the most ex pensive automatic instrumentation can not take out the nitrogen oxides from the carbon and hydrogen combustion gases, and the most sensitive and ac curate measuring method for carbon monoxide is of little use when an ir regular part of the carbon monoxide measured comes from the wall materials of the reaction tube and not from the sample. VOLUME
2 7, N O .
11, N O V E M B E R
Vertical
range
•
Vernier
reading
TOO cm
•
Working
•
Magnification
•
Level sensitive to 50
to 0.05
mm
distance 45 cm to infinity 12
χ at 45
cm—8
χ at
infinity
seconds
This cathetometer is intended f o r measurements a n d o b servations in both industrial and educational l a b o r a t o r i e s wherever an inexpensive instrument o f g o o d precision is n e e d e d . It is r i g i d l y constructed a n d e v e r y essential a d justment can be m a d e simply a n d positively. The telescope is mounted horizontally on a c a r r i a g e which may be moved up or d o w n or around the 30-mm vertical r o d . A tangent-screw adjustment permits precise leveling a n d a sensitive elevation adjustment is i n c o r p o r a t e d in the c a r r i a g e . An a u x i l i a r y level in the base g r e a t l y acceler ates the leveling process. No. 6 8 A — E a c h $ 1 9 6 . 5 0 Full-length Plastic Cover and Set o f Instructions included.
A N E of our readers across the sea has t a k e n the time to comment on the editorial in the April issue as follows:
appeared in
•
Write
for descriptive
circular.
W. M. WELCH SCIENTIFIC COMPANY Division
of W . M. Welch Manufacturing
Company
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1955
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