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XL VI. On the Mutual Solubilities of Diethylamine and Water. 

 By Robert Tabor Lattey, B.A* 



PAIRS of liquids which exhibit partial miscibility are 

 usually divided into three classes : — (1) Those which are 

 completely miscible above a certain temperature and only 

 partially miscible at lower temperatures ; (2) Those which are 

 only partially miscible at all observed temperatures ; and 

 (3) Those which are completely miscible below a certain tem- 

 perature above which they become partially miscible. 



The only cases of the third class which have been at all fully 

 studied are : sym-trimethylpyridine and water, triethylamine 

 and water (Rothmund, Zeit. Phys. Cliem. xxvi. p. 433, 1898), 

 diethylamine and water (Guthrie, Phil. Mag. xviii. p. 500, 

 1884) f. 



The case of nicotine and water recently studied by Hudson 

 [Zeit. Pliys. Chem. xlvii. p. 113, 1904) forms an interesting 

 combination of cases (1) and (3) since these liquids are com- 

 pletely miscible below 64° or above 205°, but between these 

 temperatures their mutual solubilities are only partial : the 

 solubility-temperature curve representing these phenomena 

 is a closed elliptical figure. 



This work was originally undertaken with the idea of 

 extending Guthrie's curve showing the relation between 

 temperature and the miscibility of diethylamine and water. 

 It was soon found that either Guthrie's results were incorrect 

 or that some unexpected influence was raising the tempera- 

 ture of separation. The results obtained at first were not only 

 in disagreement with Guthrie's, but were not in concordance 

 with one another. At length the behaviour of one of the 

 tubes (which happened to contain 58*6 per cent, of the amine) 

 furnished a clue to the difficulty ; the contents of this tube 

 separated into two layers at 140 0, 2, after being cooled to about 

 130° and mixed they separated at 138° ; a second and third 

 repetition of the observation gave 137° and 135° respectively. 

 Obviously some change was taking place in the contents of 

 the tube: this might either be due to an action of water on 

 diethylamine at high temperature or to the solution of glass. 

 Experiment showed that about 1 mgrm. of solid had been 

 taken up by the liquid. Experiments were therefore begun 

 in tubes of Jena glass ; the results so obtained were con- 

 cordant, and measurements made on individual tubes did not 

 differ from one another more than observations of a melting- 

 point usually differ. 



* Communicated "by the Author. 



t The case of dimethylamine and water, given by Prof, van't Hoff in 

 his " Lectures on Theoretical and Physical Chemistry," is a misprint. 

 (Private communication.) 



Phil. Mag. S. 6. Vol. 10. No. 57. Sept. 1905. 2 E 



