SECTIONAL TRANSACTIONS.— B. 401 



spectrographic method is available especially for the determination of 

 minute quantities of various elements in biochemical, agricultural, and 

 general chemical analysis. More recently we have utilised infra-red 

 spectroscopy in such determinations as the proportions of o- and p-hydroxy- 

 diphenyl sometimes found present in traces in synthetic phenol. 



For the purposes of demonstration two methods, now much used in our 

 laboratory, have been chosen. The first is the determination of moisture 

 by means of the variation in the dielectric constant. This method is 

 particularly suitable when large numbers of similar products, e.g., cereal 

 powders, have to be examined for moisture. The apparatus must be 

 calibrated for each kind of material and with suitably devised cells deter- 

 minations can be made readily in a few minutes, thus enabling products to 

 be sorted out rapidly. 



Extension of the method to liquids is obvious and apparatus is on the 

 market for the purpose. It should be noted that the usual form of apparatus 

 fails when the moisture is high and electrolytes are present. 



A second method is the polarographic method associated with the name 

 of Heyrovsky. An apparatus has been devised whereby the curves are 

 plotted by means of a recording pen, thus dispensing with the necessity for 

 visual or photographic recording. It must be stressed that in work of this 

 kind calibration of the apparatus is essential for the problem in hand. This 

 applies equally to many other physical methods, e.g. colorimetric and 

 nephelometric determinations. 



Prof. Walther Gerlach. — Spectrochemical analysis with special 

 reference to biological preparations {Demonstration) (10.30). 



Prof. Fritz Feigl. — Inorganic and organic spot-analysis {Demonstra- 

 tion) (11. 15). 



The so-called spot-analysis is a microchemical technique of qualitative 

 analysis ; it consists in the application of highly sensitive reactions to the 

 detection of inorganic and organic compounds in one drop of solution or 

 with traces of the solid substance. Such spot tests are carried out by 

 mixing one drop of the solution and one drop of the reagent on filter paper 

 or in small crucibles or on the so-called spot plates. Filter papers which 

 are impregnated with the particular reagent are very useful. The special 

 apparatus required is very simple. By means of spot analysis it is possible 

 to carry out specific detections on minute amounts of material and to 

 recognise quantities down to fractions of a millionth of a gram. The 

 saving in material, time and work is the predominating characteristic of 

 spot analysis. 



The right choice of suitable reactions is of importance. Only such 

 reactions as are sensitive and specific are used. Therefore the theory of 

 spot analysis is bound up with the chemistry of so-called specific reactions 

 and with all measures whereby sensitivity can be increased. Of great 

 importance are the application of organic reagents, the employment of 

 catalysis and the use of colloidal and capillary phenomena. The formation 

 of fluorescent compounds is also used. 



Dr. Janet Matthews. — Microanalysis (11.35). 



Inorganic micro-methods of quantitative analysis are now sufficiently 

 developed to warrant their adoption in both research and technical problems. 

 The filter stick technique has been successfully used already in problems 

 of plant nutrition in growth experiments with barley. Without the use of 



