Mutual SoluhiUty oj Liquids 



G43 



bromine and stroncr potash, collected over mercury in a 

 Bimsen ojasometer and dried over phosphorus pentoxide before 

 being admitted into the experimental tubes. It was found to 

 be but moilerately pure, a considerable pressure being required 

 for complete liipu't'iiction at some distance below the critical 

 temperature- Attempts at further purification by liquefaction 

 and partial distillation had not the desired effect. Some of 

 the data obtained for the purest sample are contained in the 

 followincr Table II. 



Table 



II. — Propane. 



Temp. 



K' 



! 



90-35 



37-4 



38-8 



95-1 



40-9 



41-9 



970* 



40.00 critical 

 ^-^^ point 



Although not so pure as ethane, the propane was still 

 sutficiently pure for an investigation of the mixtures with 

 methyl-alcohol. 



On compressing propane in the presence of methyl-alcohol 

 a second liquid layer was formed ; the three-phase pressure 

 appeared to diff'er very little from the vapour-pressure of 

 propane, and the impurities referred to above prevented a 

 decision of the question whether the pressures were lower or 

 higher than for the pure hydrocarbon. Mixtures of methyl- 

 alcohol with ethane have lower pressures than ethane, mixtures 

 with pentane and hexane have higher pressures than the 

 hydrocarbons themselves (see below). But the question is 

 capable of being answered by indirect evidence. It is well 

 known that if the three-phase pressure is above the pressures 

 of both components, the composition of the vapour is inter- 

 mediate between those of the two liquid layers ; if, on the 

 contrary, the three-phase pressure is intermediate between 

 the pressures of the components, the vapour composition lies 

 outside the liquid compositions, i. e. the vapour contains more 

 of the volatile component than either of the liquids. These 

 rules need not hold if a maximum vapour-pressure exists 

 between the three-phase pressure and either of the components, 

 as is actually the case with phenol and water ; but we will 

 assume that such a point does not exist for propane and 

 methyl-alcohol. 



* Olszewski (Bulletin St. Fetersbourg, 1889, p. xxvii) ibund 97° and 

 44 atmospheres. 



