. The London, Edinburgh and Dublin philosophical magazine and journal of science. as absolutely con-stant, and the cleaning of the tube and flushingand drying of the electrodes was extremelyeasily done. The minimum of the sound in the telephonewas very sharp if the resistance used was somehundred ohms. If smaller resistances wereused, a condenser of suitable capacity had tobe added on the side of the rheostat. The resistance-cell was put, in a largervessel filled with water, stirred by a mecha-nical stirrer, the temperature being measuredby two mercury thermometers. The resistance-cell was cal
. The London, Edinburgh and Dublin philosophical magazine and journal of science. as absolutely con-stant, and the cleaning of the tube and flushingand drying of the electrodes was extremelyeasily done. The minimum of the sound in the telephonewas very sharp if the resistance used was somehundred ohms. If smaller resistances wereused, a condenser of suitable capacity had tobe added on the side of the rheostat. The resistance-cell was put, in a largervessel filled with water, stirred by a mecha-nical stirrer, the temperature being measuredby two mercury thermometers. The resistance-cell was calibrated with a N-—. solution of potassium chloride, the specific molecular conductivity of which was adopted as 1147 . 10 _8f in termsof mercury. The distilled water used had a conductivity0*9. 10-10, which (according to Kohlrauschs Leitfaden Physik, viii. Aufl. 1896) may be considered as verylow. The freezing-points of different solutions were observed by * W. Saposchnikoff, Journ. rusk, jihys. chem. Ges. 25. ii. p. 626 (1893).t Kohlrausch, Wied. Ann. xxvi. p. Freezing-points of Solutions of Water in Formic Acid. 11 means of Beckmanns apparatus on a mercury thermometer(J. Hicks, London) divided in ^q°, corrections of which weregiven by the Kew Observatory. Solutions of water in formic acid were prepared in a glassbottle (of 50 c. c.) with a glass stopper, by weighing thebottle, then the bottle and the acid, and finally weighing thewhole, when some drops of water had been very carefullyadded. I first tested whether the formic acid, which is very hygro-scopic and easily decomposes, remained in a constant statefor the time (some hours) during which the observations ofthe resistances and freezing-points were taken. The best wayto test this is, of course, by the measurement of the resistanceof the acid during some days. The following table (Table I.) shows three such observationsfor three different solutions, freezing at 7*69, 5*4:6, 5*38respectively: — Every me
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