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Barium sulphate precipitates, formed by four different analytical methods, dried and ignited at different temperatures, have been examined with an electron microscope. The study of the dissolution of precipitates has been found useful for the investigation of thermal aging. On heating the precipitates, diffusion, which takes place at temperatures depending on structure, permits structural changes such as reordering to take place. Consequently, the structure of the ignited precipitates approaches the ideal arrangement.

Thirteen sodium salts have been investigated derivatographically. The weight change, rate of weight change and enthalpy change of the salts have been measured as a function of temperature. The temperatures at which the salts may be dried without decomposition are given. Some of the curves are explained in terms of the effects of heat and gaseous products on the structure of the salts.

Tungsten can be precipitated by a solution of Variamine Blue at pH 5. The precipitate is ignited to constant weight at a temperature above 600 degrees and weighed as tungsten trioxide. The method can be used for the determination of tungsten in alloy steels.

This review gives a survey of the theoretical considerations which led to the introduction of derivative methods in thennoanalysis, and of the development of complex thennoanalytical methods. The paper introduces the method of derivatography and its development, and surveys the wide field of its application in chemistry, technology, physical chemistry and biology.

The acid and base dissociation constants of luminol are determined at various ionic strengths. The transition interval occurs at pH 7.7-9.0, therefore luminol is a fluorescent indicator for the titration of strong and weak acids and strong bases. Its value as an indicator is established by titrating milk, red wine and cherry juice.

A device for the continuous introduction of powdered samples into spark and arc sources is described. The sample is pushed by a motor-driven spindle into the electrode gap through a tubular electrode. The method was found to be simple and versatile.

A method is given for the amperometric determination of thioacetamide (TAA) based on the reaction of TAA with copper(I) in ammoniacal solution. The reduction current due to the copper(I) is used to determine the end-point. The determination is carried out at constant temperature (25 degrees ), pH 8.0-9.8 (ammonia-urotropine buffer), and at constant potential (-0.6 V vs. S.C.E.), with a dropping mercury electrode as cathode and a saturated calomel electrode as anode. The solution is deaerated by a stream of electrolytically generated hydrogen. The titrations are carried out simply and rapidly and the results are fairly reproducible. The error is generally 1.0% for amounts of TAA ranging from 0.07 to 1.8 mg.

A rapid method is described for the simultaneous determination of 2,4-tolylene diamine and 2,4-tolylene diurea by infrared spectroscopy. The method is satisfactory for the diurea determination but gives rather large errors in the diamine determination.