Hydrochloric Acid and Methylether. 597 



broadness of some of the condensation loops of which the 

 loop in the figure for a mixture of 7 per cent, ether to 93 per 

 cent, acid shows a striking example. Near the minimum the 

 loops are necessarily very narrow, and therefore also between 

 B and 6\ : this is not the case with the mixtures between B 

 and C 2 , at least not with those some distance away from B. 

 For a mixture like the one in the figure the two critical points 

 P and R must be far apart from each other and from the 

 critical point (not shown in the figure) which the mixture 

 would have if it did not separate into two phases of different 

 composition, but behaved like a single substance*. With 

 mixtures of maximum vapour-pressure and minimum critical 

 temperature, such as ethane + nitrous oxide, which were dis- 

 covered some time ago, the loops between B and the critical 

 point of ethane were broader than the others, but even there 

 remained relatively narrow ; and it was natural then to suppose 

 that this fact, had greater generality than now appears to be 

 the case. The shape of the plaitpoint curve and the great 

 distance between B and C 9 in this case might have suggested 

 the probability of broader loops, even without the confirmation 

 by experiment. 



It is unnecessary to indicate the shape and changes of 

 the plait on the "^-surface for mixtures of hydrochloric acid 

 and methylether, as we can refer the reader to Hartman's 

 thesis quoted above. 



As regards the experiments themselves, I will only mention 

 that the methylether was prepared from pure methylalcohol 

 and sulphuric acid, and absorbed in sulphuric acid from which 

 it was afterwards liberated by water. 1 refrain from com- 

 municating all the numerical data obtained, as no value can 

 be attached to the results except qualitative value. Mr. 

 W. G. Robson assisted me during the whole of the 

 investigation. 



The question what is the molecular condition of the mix- 

 tures seems as yet hardly capable of satisfactory solution. 

 The criteria which are applied for this purpose with regard 

 to single substances fail with mixtures. It was lately pointed 

 out by Kamerlingh Onnes f that the law of corresponding- 

 states cannot without further consideration be applied to 

 mixtures; and van der Waals's equation deviates too much from 



* Compare van der Waals, Kon. Ah. Amsterdam, 27tli November, 1897. 



f Kamerlingh Onnes, Km. Ah. van Wet. 30 June, 1900. In this 

 paper mixtures without mutual association are called u ideal " mixtures : 

 " normal '' mixtures seems more in accordance with the common use of 

 the two words. 



