SOME PROBLEMS OF ATMOSPHERIC CHEMISTRY* 
By H. CAUER 
Institute for Chemical Climatology, Hohenberg a. d. Eger, Germany 
INTRODUCTION 
Although a good basis for chemical investigations in 
the atmosphere was established during the past century 
by Smith [53], and individual investigations such as 
those by Schmauss and Wigand [51] have been of great 
value, a full incorporation of chemical concepts and 
procedures into the consideration of meteorological phe- 
nomena has not, up to the present, become general. 
This is due primarily to the fact that satisfactory meth- 
ods for the chemical analysis of air do not yet exist, 
and furthermore that none of the available methods 
lend themselves to the routine procedures which have 
been possible in the measurement of physical phe- 
nomena. At present, experimental work of this kind 
requires a good chemical-analytical knowledge and 
many years of experience if passably reliable results 
are to be obtained. Since the pertinent methods con- 
sist of special techniques for detecting traces, their 
mastery cannot be expected by physicists, even those 
whose minor field is chemistry or physical chemistry. 
On the other hand, although the analytical chemist has 
the necessary specialized knowledge, including the 
requisite information in the physico-chemical field, he 
lacks a fundamental insight into the problems of physi- 
cal meteorology. 
Therefore, the most important task in the develop- 
ment of chemical meteorology and climatology appears 
to the author to be the training of analytical chemists 
who study physical chemistry and physical meteorology 
as secondary fields. A second requirement, and one 
which will necessitate the active participation of the 
analytical chemist, is the further development of meth- 
odology. Not until the development has been more or 
less completed will it be possible to undertake a third 
major task, that of making many parallel investigations 
in micrometeorological as well as world-wide networks 
under the most varied atmospheric conditions and at 
various heights above the ground. 
METHODS 
As a survey of the chemical methods available today, 
two groups of methods developed in Hurope will be 
discussed briefly: (1) the absorption-tube method for 
detecting the presence of secondary gaseous substances, 
and (2) the condensation method for the analysis of 
water-soluble constituents of the air which form con- 
densation nuclei. 
Absorption-Tube Methods for Detecting Traces of 
Gaseous Materials. The iodine of the air is determined, 
in principle, according to the method developed by von 
* Translated from the original German. 
Fellenberg [25], that is, by absorption in a very dilute 
aqueous K.CO; solution and final determination by 
colorimetric or titrimetric techniques. This method has 
been greatly simplified by the author with the apparatus 
shown schematically in Fig. 1. It consists of a motor- 
driven pump, dry-gas meter, and Cauer absorption 
tube. As a result of control investigations by Quitmann 
[44], this equipment has been simplified and can be 
used for serial and uninterrupted tests. It is made in 
three sizes [7]: an apparatus mounted on a stand 
equipped with an absorption tube (circulation capacity 
10 m? hr); a readily portable apparatus provided with 
an absorption tube (circulation capacity 0.6 m® hr); 
and a smaller apparatus for measuring small amounts. 
The use of this equipment has been described else- 
where [5]. The chemical analysis requires 60-90 min. 
Fra. 1.—Schematic representation of apparatus for detect- 
ing traces of gaseous materials; (a) Cauer absorption tubes 
without separate charging vessel; (b) motor and pump; (c) 
dry-gas meter. 
Depending on the concentration present, the total 
chlorine (chloride, free chlorine, chlorine dioxide) is 
determined, according to Cauer [6], with one of the 
devices mentioned above, using a 1.5 per cent solution 
of KOH. Final determination is made by titration 
with AgNO;. According to the data given by Nitschke 
[41], best results are obtained in alcoholic solution after 
the method of Bang and Blix. One-sixth of the free 
chlorine escapes analysis. The air sampling requires 
10-60 min, the chemical analysis about 1 hr. 
The sulfuric acid or the sulfates and sulfites are de- 
termined by two methods. The first is a nonquantitative 
standard method developed by Liesegang [38], which 
measures the quantity of sulfates plus sulfites precipi- 
tated during a period of 100 hr on a porcelain bell 
equipped with an extraction thimble. The end deter- 
mination is made gravimetrically as BaSO.. The method 
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