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The coagulation rate of an aqueous salt solution aerosol of Na2SO4has been determined in terms of number and mass concentration under various conditions, with the finding that the rate constant in mass concentration might be useful as a measure of coagulation rate. Some examples of its application are described in detail.

By atomizing aqueous solutions both of electrolytes and non-electrolytes, fog droplets of 8µ in diameter were prepared, and their freezing temperatures were measured in a thermostat-like cold chamber fitted with an electrically heated platinum wire. The results were compared with that obtained with fog droplets of pure water of the same size. It was found that non-electrolytes hardly influence the freezing, whereas electrolytes do a great deal. The freezing temperature rises in the presence of an electrolyte and varies with its concentration, the highest temperatures being observed at the concentrations around 1×10-4mfor 1-1 type electrolytes and at lower concentrations for 1-2 and 1-3 type electrolytes. K+is the most effective of the alkali metal cations having the same species of anion in common, and I-of the halide anions having the same species of cation in common. Applying the theory of nucleation, the sizes of the hydrated K+and the critical nucleus developed from it for ice-nucleation were estimated to be about 6 and 21 Å in radius, respectively.

(1) The catalytic decomposition of hydrogen peroxide by colloidal platinum-carbonyl as well as colloidal platinum obtainabe from it was examined.(2) In the former case, the reaction proceeds as unimolecular after it passed through an induction period, while in the latter case, it deviates apprecialy from unimolecular throughout the course of the reaction concerned.(3) Some considerations were made on these facts.

(1) By passing carbon monoxide gas through the dilute aqueous solution of chloroplatinic acid, a red-coloured colloidal solution was obtained.(2) The red sol was more stable than the ordinary black platinum sol against electrolytes.(3) The red sol changed to the black one evolving some gas bubbles by the action of air, oxygen, hydrogen peroxide, alcohols, and aceton, or by the process of evacuation or heating.(4) The action of bromine water on the red sol is described.(5) The change of the electrical conductivity was measured in the process of formation of the red sol.(6) The structure of the colloidal particles of the red sol is discussed. They consist, probably, of groups of platinum carbonyl molecules.

(1) The decomposition of aqueous solutions of oxalic acid (0.10, 0.05, 0.025 N) due to oxidation accelerated by colloidal platinum-carbonyl of red colour as well as colloidal platinum of black colour obtainable from it was, in the presence of oxygen and diffused day-light, studied during a period extending several hundred hours at 25.0 °C. and thirty hours at 50.0 °C.(2) In the case where the red sol is added as catalyst, the reaction proceeds as unimolecular after it passed through an induction period and subsequently a transition period, while in the case where the black sol is added, it proceeds as the above after a transition period, no induction period presenting itself.(3) The more dilute the acid solution, the more stable is the sol throughout the course of the experiment and consequently, the larger is the velocity constant.(4) The mechanism of the reaction was discussed on these facts.

(1) The influence of the temperature of preparation on the forma？ion of platinum-carbonyl sol from the chloroplatinic acid solution by the action of carbon monoxide were investigated at various temperatures between 5° and 80°C., together with the influence of the concentration of solution ranging from 0.01 to 0.1% with respect to H2PtCl6·6H2O.(2) Stable sols having a tinge of red with a dash of purple may be produced from the solutions of concentrations between 0.01 and 0.08% in a wide range of temperature; sols of various colours such as brownish red, brown as well as dark brown may be formed in the same limits of concentration as the above at the elevated temperatures.(3) Sols tinged with red slightly inclining to purple may be obtained, though unstable, from the 0.1% acid solutions only at lower temperatures.(4) The colouration effects above-mentioned were spectroscopically analyzed with the Nutting’s spectrophotometer, and it was found that the extinction curves for the sols tinged with red reach a maximum at about 540 mμ, while those for the sols with a tinge varying from brown to black decrease monotonously with the increasing wave-length.

(1) The decomposition of aqueous solutions of oxalic acid (0.10, 0.05 and 0.025 n) due to oxidation accelerated by colloidal platinum obtained through the process of dialysis of colloidal platinum-carbonyl was investigated, in the presence of oxygen and diffused day-light, during a period extending over thirty hours at 50.0°C.(2) It appears that the greater part of the course of reaction proceeds in accordance with the formula for the type of zero order after it passed incipiently through a short period of transition and the rate of reaction is scarcely influenced by the concentration of reacting solution.(3) It was definitely shown that the reaction should be retarded if the supply of oxygen is cut off.(4) The above results were explained in conformity with the mechanism of reaction previously proposed.

A substance was purified from urine of rats treated with an inhibitor of aldehyde dehydrogenase (aldehyde: NAD oxidoreductase, EC 1.2.1.3) and histamine and was identified as imidazoylethanol (4(5)-imidazoyl-ethane-2-ol) by means of ion-exchange chromatography, paper chromatography, paper electrophoresis and qualitative reactions and also by the conversion into histamine and imidazolethylacetate. A compound having the same characteristics as imidazoyl ethanol was detected as a normal constituent in the urine of men and rats.

Droplets of aqueous NaCl solution aerosols generated by atomization were collected on an AgNO3containing film, by measuring microscopically the sizes of the AgCl spots formed on the film, the diameters of the droplets were determined with the aid of the calibration curve between the spot and droplet diameters. It was found that the calibration curve can be expressed by a relation Dd3=Kds2, where Ddis the volume average diameter of the droplets, dsthe surface average diameter of the spots and Ka constant. The meaning of Kwas considered.

An aqueous NaCl solution (10%) containing a surface active substance was dispersed to a mist with a Dautrebande type atomizer. The influence of the surface active substance on the droplet size and mass concentration of the mist during aging was studied. We examined ethyl alcohol, acetic acid, ethyl acetate, acetone, glycerine, and a commercial nonionic surfactant. From the results it was found that at an early stage of aging, the droplet number present in mist was inversely proportional to the fourth power of droplet size.

The aerosols obtained by spraying an aqueous Na2SO4solution of concentrations ranging from 0.1 to 10% by weight were dried by a furnace at 200 to 800°C and were then subjected to stirred aging at room temperature in an atmosphere of 90% relative humidity or less; the variations in both mass concentration and particle size were then measured with the lapse of time.By employing the results thus obtained and by making some assumptions, the density of the particle in dried aerosols was calculated to be several tenths of one gram per cc, which is smaller by a factor of 3 to 4.5 than the bulk density of solid Na2SO4; further, the amount of water which the dried particle might hold if kept in a humidified atmosphere was estimated, with the finding that the density of a particle would decrease with increase in its water content; for example, the density of the particle with composition of Na2SO4·10H2O would be 0.32 g/cc, smaller by a factor of 4 to 5 than the bulk density. In addition, the influence of water vapor on the stability of the dried aerosols was studied; it was found that the higher the humidity, the greater the rate of coagulation.