ON SOLUBILITY. 431 



The apparatus was weighed before and after saturation, and the differ- 

 ence gave the amount of ammonia absorbed. 



.o 7fi Setschenoff 65 used a similar method to that of Fernet, but 



connected the measuring and absorption vessels by a flexible 

 capillary of silver, so that the absorption bulb could be shaken without 

 disconnecting it. 



-^ 7 „ Mackenzie r,G made use of an absorption tube divided into two 



parts by a stop-cock and immersed in water. The lower part was 

 filled with solvent and the upper part with gas at the requisite pressure, 

 which was measured by a separate manometer. The stop-cock was 

 opened and the gas and solvent shaken together. The absorption tube 

 was again joined to the manometer and mercury allowed to flow into 

 the absorption tube until the original pressure was attained. These 

 operations were repeated until no more mercury entered the absorption 

 tube. The volume of mercury in the absorption tube, obtained by 

 weighing the dry mercury, gave the volume of gas dissolved. 



To expel the gas from a saturated solution and at the same time to 

 measure its volume Hiifner 69 devised a special form of Sprengel pump. 

 mft9 WroblewsH 94 described a form of absorptometer he used to 



measure absorption coefficients up to 60 atmospheres, the pres- 

 sure being determined by means of an air-manometer. 

 ■.004. Roozeboom 110 passed hydrogen chloride gas into water at a 



*" " temperature about 2° C. lower than the final temperature : the 

 temperature was allowed to rise gradually and then maintained within 

 (P.l C. for fifteen minutes. 



Lubarsch 11S used a modified form of Lunge's nitrometer to 

 collect and measure the volume of gas expelled from saturated 

 solutions by evacuation. 



Pettersson 153 described an apparatus for boiling out and measuring 

 the volume of a gas in solution. In the hands of Pettersson and 

 Sonden 154 this apparatus gave very concordant results. 



In passing gases through liquids, Winkler 1S& measured the height 

 of the level of solvent above the end of the inlet tube, and added half 

 the pressure due to this height to the barometric pressure to obtain 

 the partial pressure of the gas. 



Timofejew 163 gave a detailed description of the use of an appa- 

 ratus similar to that employed by Fernet (vide this Section 1857). 

 Doyer 166 measured the quantity of dissolved substance carried out 

 of solution by a known volume of air passed through the solution, and 

 from this calculated the partial pressure corresponding to a given 

 strength of solution. The absorption coefficients were found by this 

 means for gases' and also for substances which are liquid at ordinary 

 temperatures. 



A differential absorption apparatus was described by Bohr a nd 



Bock, 167 in which the measurement of the partial pressure of 



the gas was directly determined, independent of the vapour pressure of 



the solvent. By this means absorption coefficients were obtained with 



increased accuracy up to 60° C. 



Pryty and Hoist 231 passed carbon dioxide gas through, or 

 ^ added solid carbon dioxide to water contained in a flask. The 



F F 2 



