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The effect of dissolved substances on the deposition of colloidal particles from a solution by means of an electric current
March, I923. ]
CURRENT TOPICS.
42I
notes were very accurately transmitted. Men's voices are better understood than those of women. Resonators augmenting the volume of sounds at the same time modify them to a great extent. G. F. S. The Effect of Dissolved Substances on the Deposition of Colloidal Particles from a Solution by Means of an Electric Current. R. D. KLEEMAN. (Phys. Rev., Sept., ~922.)--Porcelain slip is a colloidal solution in water of particles of flint, feldspar and clay. " D u r i n g some experiments on the electric deposition of porcelain slip it was observed that the deposit obtained from the slip used in the wet porcelain process was solid though not quite dry, while that obtained from slip used in the dry process was of the consistency of thick cream. It was soon found that the difference in the nature of the deposits obtained was due to the small quantity of sodium silicate (Na..SiO:~) that is mixed with the slip used in the wet process. It was found that besides sodium silicate the substances Na.,SO,, Na:~PO,, Na.~HPO4, H tartrate, Na tartrate, N a O H , K O H showed the effect very well, and in fact it was found that most substances showed the effect in a m o r e or less degree." The compactness of the deposit in general increases with the quantity of substance added though with a small added amount (one part in from 3oo to Iooo by weight), the maximum effect is attained, and further increase produces no noticeable result. The current density seems to be without effect on the hardness of the deposit, unless sufficient gas is evolved to interfere with the process. There is a connection between the foregoing effect and the following. Let a slip be taken which holds 3° per cent. of solid matter by weight. To this add one three-hundredth of Na:~PO4. Solid matter will be deposited, mostly feldspar and flint. This precipitate will, however, go again into solution upon the addition of further solid matter. When enough of this has been added to make the fluidity the same as before the introduction of Na:~PO4, the slip will be found to contain about twice as much solid matter as before. " Both effects may be explained if we assume that the radii of the spheres of action of the particles of the slip are diminished by the dissolved substance. It is concluded that the volume of the sphere of action of a particle in porcelain slip is about double the actual volume." G.F.S. Progress in Nitrogen Fixation.--The annual report of the United States laboratory for research on nitrogen fixation gives a summary of the work accomplished in the fiscal year ending June 3o, I922. The laboratory is under the direction of Doctor Cottrell, and is in the Department of Agriculture. The importance of the procedures for nitrogen fixation is pointed out. Three of these are at
CURRENT TOPICS.
42I
notes were very accurately transmitted. Men's voices are better understood than those of women. Resonators augmenting the volume of sounds at the same time modify them to a great extent. G. F. S. The Effect of Dissolved Substances on the Deposition of Colloidal Particles from a Solution by Means of an Electric Current. R. D. KLEEMAN. (Phys. Rev., Sept., ~922.)--Porcelain slip is a colloidal solution in water of particles of flint, feldspar and clay. " D u r i n g some experiments on the electric deposition of porcelain slip it was observed that the deposit obtained from the slip used in the wet porcelain process was solid though not quite dry, while that obtained from slip used in the dry process was of the consistency of thick cream. It was soon found that the difference in the nature of the deposits obtained was due to the small quantity of sodium silicate (Na..SiO:~) that is mixed with the slip used in the wet process. It was found that besides sodium silicate the substances Na.,SO,, Na:~PO,, Na.~HPO4, H tartrate, Na tartrate, N a O H , K O H showed the effect very well, and in fact it was found that most substances showed the effect in a m o r e or less degree." The compactness of the deposit in general increases with the quantity of substance added though with a small added amount (one part in from 3oo to Iooo by weight), the maximum effect is attained, and further increase produces no noticeable result. The current density seems to be without effect on the hardness of the deposit, unless sufficient gas is evolved to interfere with the process. There is a connection between the foregoing effect and the following. Let a slip be taken which holds 3° per cent. of solid matter by weight. To this add one three-hundredth of Na:~PO4. Solid matter will be deposited, mostly feldspar and flint. This precipitate will, however, go again into solution upon the addition of further solid matter. When enough of this has been added to make the fluidity the same as before the introduction of Na:~PO4, the slip will be found to contain about twice as much solid matter as before. " Both effects may be explained if we assume that the radii of the spheres of action of the particles of the slip are diminished by the dissolved substance. It is concluded that the volume of the sphere of action of a particle in porcelain slip is about double the actual volume." G.F.S. Progress in Nitrogen Fixation.--The annual report of the United States laboratory for research on nitrogen fixation gives a summary of the work accomplished in the fiscal year ending June 3o, I922. The laboratory is under the direction of Doctor Cottrell, and is in the Department of Agriculture. The importance of the procedures for nitrogen fixation is pointed out. Three of these are at