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Physics. — „ Tlie influence of pressure en the critical temperature 

 of complete mixture". By Mr. N. J. van der Lek. (Com- 

 niunicated by Prof. J. D. van der Waals.) 



Ia 188G (Wied. Ann. Bd. 28) Mr. Alexejew published investi- 

 gations, undertaivon to find out the influence of temperature on the 

 mutual solubility of two liquids which are but partly soluble in 

 each other. A temperature proved to exist, above which mixture in 

 all proportions takes place (critical temperature of complete mixture). 

 The existence of this temperature had been already supposed before. 

 In 1880 (Verb. Kon. Ale), Prof, van der Waals had pointed out, 

 that the pressure too, must play a part in this phenomenon, and 

 ho had found that in a mixture of etlior and water, the meniscus, 

 parting the two phases, becomes flatter by higher pressure. Though 

 this might be considered as a proof that the two phases approached 

 each other as far as composition is concerned, complete mixture is 

 not attained. Mr. Alexejew seems to have been induced tiirougli 

 this treatise, to examine also the influence of pressure for the mixtures 

 investigated by him, but with a negative result. (I have not been 

 able to consult the description of these last experiments. I know 

 them only from citations). By the theory of the surface ip (J. D. 

 VAN DER Waals: „Theorie moleculaire d'une substance composée 

 de deux matières difïérentes. Arch. Néerl. T. 24 or Versl. Kon. Ak. 

 23 Febr. 1889) the influence of the pressure on the mutual solubi- 

 lity was also examined. In 1894 Mr. J. de Kowalsky published 

 the description of his investigations (C. R. T. CXIX p. 512) concer- 

 ning this theory. No influence of the pressui'e was found — not 

 even by very high pressures — except for a triple mixture of 

 aethylalcohol, isobutylalcohol and water. A pressure of 900 atm. 

 made the liquid homogeneous at a temperature of about 3° below 

 the temperature of complete mixture. Of late Mr. Klobbie (Zeitschr. 

 f. phys. Chem. 24. 617. 1S97) has found a perceptible influence of 

 the pressure for mixtures of ether and water by a pressure of 100 

 atmospheres, without, however, determining its degree. 



The purpose of the experiments which will be described here, 

 was, to find something about the influence of the pressure on the 

 mixture of liquids. 



Of all the mixtures examined by Mr. Alexejew the pair water 

 and phenol seemed best fitted for these investigations. The critical 

 temperature of complete mixture is about 67°. The phenol used 

 was from Merck & Co. and was tested beforehand by determining 

 the fusing-point. It was preserved in the dark in sealed glass tubes, 



