:^(i9 



obtained, whereas another solvent always yields the stable modification. 



If, tlierefore, the line for the internal equilibrium as Fig-. 2 shows, 

 lies above L, i.e. if at the considered temperature B„ is stable, and 

 7>(, and L\ lie greatly on the ^-side, then for the same reason the 

 possibility is to be expected that when B„ is dissolved in C, the 

 metastable modification A„ deposits from the supersaturate solntion 

 at lower temperature. 



Where this phenomenon presents itself it will be an interesting 

 problem to determine the situation of the points L, />„, and L\ at 

 a definite temperature, to find out in this way in how far the given 

 explanation is the true one. 



Amsterclinn, 24 June 1915. Anorij. Clwiii. Ltth. of ihe Universiti/. 



Chemistry. — • "Super saturation and release of siipersaf/nnfioit." 

 By Dkvendra Nath Bhattacharyya and Nii,ratan Dhak. 

 (Communicated by Prof. Ernst Cohkn). 



The older literature on snpersatiiration, chiefly works of Gay 

 Lussac '), ScHWEiGGER "), Ziz '), THOMSON "), Ogden^), and others, 

 abounds with evidences showing that the piienomenon is rather 

 common. 



But after that, the general idea of the chemists was that only 

 few substances could form supersaturated solutions. 



But now a days chemists have recognised again that the pheno- 

 menon is common. Thus Mendei.kbff [Principles of Chemistry, English 

 translation (1905), p. 93] states that salts which separate out with 

 water of crystallisation and form several crystalloliydrates yield 

 supersaturated solutions with the greatest ease, and the phenomenon 

 is much more common than was previously imagined. Ostwald 

 has studied this case very thoroughly and is of opinicm that this is 

 very common. Tutton also mentions in his book, "Crystals" (p. 238) 

 that supersaluiation is a phenomenon of frequent occurrence. 



But the reminiscence of the old idea is still unconsciously present 

 in the popular mind. For demonstration exjierimenls, sodium acetate, 

 or sodium sulphate, or sodium lliiosulphate is invariably taken. Also 



i) Ami. Gliim. 87, 225; Sthw. 9. 70; Ann. Cliim. Pliys. 11, 301. 

 -) Schw. 9, 79. 



5) Schw. 15, 160. 



1) Ann. Phil. 19, 169. 



6) N. Ed. Phil. J. 13, 309 



