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782 CURRENT TOPICS. [J. F. I. Action of Colloids on Radio-active Products in Solution. T. GODLEWSKI. (Phil. Mag., xxvii, 618.)--It has been previously shown that the products of the active deposit of Ra in neutral, alka- line, or weakly acid solutions are in the colloidal state. It was also found that in acidulated solutions or in presence of polyvalent cations the products were deposited at the cathode almost exclusively, while in presence of polyvalent anions the anode is activated on electrolysis. Anomalous results were obtained with RaC, which in pure water solution appears to be deposited partly at the cathode and partly at the anode, although RaA appears at the anode only, and RaB at the cathode. Further experiments appear to explain this. When the atom of RaC arises from the RaB the recoil is only feeble, RaB emitting only a ~ particle. For this reason, if one of the atoms in the aggre- gate RaB which forms the centre of a positive hydrosol is trans- formed into RaC, it will not escape from its environment of RaB atoms, but will be carried with them to the cathode. We may, there- fore, expect that only those RaC atoms go to the anode which man- age to escape during their transformation, and also those which belong to groups in which the majority of the RaB atoms have already undergone transformation. Detailed experiments have been made on the influence of foreign colloids on the hydrosols of RaA, RaB, and RaC. The results show that the addition of a negative colloid (arsenious sulphide or platinum) in small quantity causes the products deposited at the cathode to diminish in amount and afterwards to disappear. Similarly, positive colloids (ferric oxide) when added in relatively small amount conduce to precipitation of RaA and RaC, which are among negative colloids; in higher concen- trations positive colloids absorb them, thus inverting their signs. Radio-active products, as positive hydrosols, can be concentrated by filtration, since these hydrosols are entrained by filter-paper, owing to capillary action. Durability of Taps for Benzine Tanks. ANOy. (Eng., xcviii, No. 2532, 63.)--Professor Alexander Baumann, of the experimental station for a~ronautics and automobilism of the Technical High School at Stuttgart, has made some experiments on the durability of taps, greased and ungreased, when exposed to the flow of benzine. New taps were fitted into two vertical pipes, each three metres high; the upper portions of the pipes consisted of glass tubes, 4 mm. in internal diameter, behind which cardboard scales were fixed. By the aid of mechanism the two taps were opened and closed simul- taneously, fifty times in each series, and observations were taken half an hour later of the sinking of the benzine level. The one tap was greased and the other not. The loss of benzine with the greased tap amounted to 5 mm. or less, and did not increase. With the un- greased tap the loss amounted to I45 mm., and rose in later trials to I5OO ram. Nothing is said as to the nature of the grease used; it is merely stated that it should be insoluble in benzine.

Durability of taps for benzine tanks : Anon. (Eng., xcviii, No. 2532, 63)

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Page 1: Durability of taps for benzine tanks : Anon. (Eng., xcviii, No. 2532, 63)

782 CURRENT TOPICS. [J. F. I.

Action of Colloids on Radio-active Products in Solution. T. GODLEWSKI. (Phil. Mag., xxvii, 618 . ) - - I t has been previously shown that the products of the active deposit of Ra in neutral, alka- line, or weakly acid solutions are in the colloidal state. It was also found that in acidulated solutions or in presence of polyvalent cations the products were deposited at the cathode almost exclusively, while in presence of polyvalent anions the anode is activated on electrolysis. Anomalous results were obtained with RaC, which in pure water solution appears to be deposited partly at the cathode and partly at the anode, although RaA appears at the anode only, and RaB at the cathode. Fur ther experiments appear to explain this. When the atom of RaC arises from the RaB the recoil is only feeble, RaB emitting only a ~ particle. For this reason, if one of the atoms in the aggre- gate RaB which forms the centre of a positive hydrosol is trans- formed into RaC, it will not escape from its environment of RaB atoms, but will be carried with them to the cathode. We may, there- fore, expect that only those RaC atoms go to the anode which man- age to escape during their transformation, and also those which belong to groups in which the majority of the RaB atoms have already undergone transformation. Detailed experiments have been made on the influence of foreign colloids on the hydrosols of RaA, RaB, and RaC. The results show that the addition of a negative colloid (arsenious sulphide or platinum) in small quantity causes the products deposited at the cathode to diminish in amount and afterwards to disappear. Similarly, positive colloids (ferr ic oxide) when added in relatively small amount conduce to precipitation of RaA and RaC, which are among negative colloids; in higher concen- trations positive colloids absorb them, thus inverting their signs. Radio-active products, as positive hydrosols, can be concentrated by filtration, since these hydrosols are entrained by filter-paper, owing to capillary action.

Durabi l i ty of Taps for Benzine Tanks . ANOy. (Eng., xcviii, No. 2532, 63 . ) - -P ro fesso r Alexander Baumann, of the experimental station for a~ronautics and automobilism of the Technical High School at Stuttgart, has made some experiments on the durability of taps, greased and ungreased, when exposed to the flow of benzine. New taps were fitted into two vertical pipes, each three metres high; the upper portions of the pipes consisted of glass tubes, 4 mm. in internal diameter, behind which cardboard scales were fixed. By the aid of mechanism the two taps were opened and closed simul- taneously, fifty times in each series, and observations were taken half an hour later of the sinking of the benzine level. The one tap was greased and the other not. The loss of benzine with the greased tap amounted to 5 mm. or less, and did not increase. With the un- greased tap the loss amounted to I45 mm., and rose in later trials to I5OO ram. Nothing is said as to the nature of the grease used; it is merely stated that it should be insoluble in benzine.