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Some geophysical problems
738
CURRENT TOPICS
[J. F. 1.
Determination of Potassium as Acid Tartrate.--R. MAURICF. describes in Ann. Chim. Ana~., etc. ([2], 1925, 7, 16i ), a procedure in which advantage is taken of the sparing solubility of acid potassium tartrate, but instead of weighing the precipitate, it is titrated with standard acid after over-neutralizing it with standard alkali. The precipitant is acid sodium tartrate dissolved in a mixture of equal parts of pure methanol and water. Methanol of high purity and almost absolute can now be obtained in abundance and at reasonable rates. If stilphates are present, sodium sulphate will separate, but as this is neutral, it will not interfere with the determination by titration. After obtaining the precipitate of acid potassium tartrate, and decanting the liquid through a suitable filter, it is washed with the methanol-water mixture until a few drops of the filtrate give no appreciable precipitate with a concentrated solution of potassium acetate. As is well known, the separation of acid potassium tartrate is promoted: by stirring, which should not be omitted. It is advisable not to use more than ioo C.C. Of the washing liquid, divided into as many small portions as possible. After washing, the filter and contents are placed in the beaker containing the rest of the precipitate, over-neutralized by standard sodium hydroxide, and the excess of alkali determined by titration with standard acid:. Test analyses with samples containing sulphates, nitrates and chlorides, as well as magnesium compounds, showed approximations to about o. 5 per cent. of the amount present. To insure the complete precipitation of the acid potassium tartrate, it is necessary to stir the liquid well and even to allow it to stand over night. The procedure is recommended for the analysis of fertilizers. H.L. Some Geophysical Problems. R. L. FARIS. (Jour. VV'ash. Acad. Sci., Aug. 19, I925.)--We speak of elevation above the sea so glibly that it comes as something of a shock to learn that mean sea-level is a hard thing to determine. " As a geophysical problem it is found to have variations from year to year, and through a period of years. Neither are all of its variations yet known nor are their causes understood in detail. So it is yet a problem of prime importance for systematic observation and study." At the 1924 meeting of the International Geodetic and Geophysical Union in Madrid the Hayford Spheroid was officially adopted, and the validity of the theory of isostasy was recognized. Doctor Meinesz, of the Dutch Geodetic Commission, has measured the acceleration of gravity on a submerged submarine, thus opening the way for other determinations on the oceans for which there is great need. There is lack of a gravity instrument that shall be easier to use in regard to the labor both of observation and of computation. It is held by some that the continents are slowly drifting like huge rafts. To find whether this is so more latitude and longitude determinations are required. G.F.S.
CURRENT TOPICS
[J. F. 1.
Determination of Potassium as Acid Tartrate.--R. MAURICF. describes in Ann. Chim. Ana~., etc. ([2], 1925, 7, 16i ), a procedure in which advantage is taken of the sparing solubility of acid potassium tartrate, but instead of weighing the precipitate, it is titrated with standard acid after over-neutralizing it with standard alkali. The precipitant is acid sodium tartrate dissolved in a mixture of equal parts of pure methanol and water. Methanol of high purity and almost absolute can now be obtained in abundance and at reasonable rates. If stilphates are present, sodium sulphate will separate, but as this is neutral, it will not interfere with the determination by titration. After obtaining the precipitate of acid potassium tartrate, and decanting the liquid through a suitable filter, it is washed with the methanol-water mixture until a few drops of the filtrate give no appreciable precipitate with a concentrated solution of potassium acetate. As is well known, the separation of acid potassium tartrate is promoted: by stirring, which should not be omitted. It is advisable not to use more than ioo C.C. Of the washing liquid, divided into as many small portions as possible. After washing, the filter and contents are placed in the beaker containing the rest of the precipitate, over-neutralized by standard sodium hydroxide, and the excess of alkali determined by titration with standard acid:. Test analyses with samples containing sulphates, nitrates and chlorides, as well as magnesium compounds, showed approximations to about o. 5 per cent. of the amount present. To insure the complete precipitation of the acid potassium tartrate, it is necessary to stir the liquid well and even to allow it to stand over night. The procedure is recommended for the analysis of fertilizers. H.L. Some Geophysical Problems. R. L. FARIS. (Jour. VV'ash. Acad. Sci., Aug. 19, I925.)--We speak of elevation above the sea so glibly that it comes as something of a shock to learn that mean sea-level is a hard thing to determine. " As a geophysical problem it is found to have variations from year to year, and through a period of years. Neither are all of its variations yet known nor are their causes understood in detail. So it is yet a problem of prime importance for systematic observation and study." At the 1924 meeting of the International Geodetic and Geophysical Union in Madrid the Hayford Spheroid was officially adopted, and the validity of the theory of isostasy was recognized. Doctor Meinesz, of the Dutch Geodetic Commission, has measured the acceleration of gravity on a submerged submarine, thus opening the way for other determinations on the oceans for which there is great need. There is lack of a gravity instrument that shall be easier to use in regard to the labor both of observation and of computation. It is held by some that the continents are slowly drifting like huge rafts. To find whether this is so more latitude and longitude determinations are required. G.F.S.