Mr. A. Liversidge on Supersaturated Saline Solutions. 75 



although he made what has since been proved to be a mistake in 

 assigning 8H 2 to the modified salt. 



The writer allowed some supersaturated solutions of sodic sul- 

 phate to evaporate spontaneously, and, after several vain attempts, at 

 last succeeded in obtaining good crops of such crystals, without ad- 

 mixture of the normal salt, which, of course, is liable to crystallize out 

 also on opening the receiver. The ring of crystals at the top of the 

 solution only were taken. 



Results of determinations of water of crystallization in crystals 

 of sodic sulphate formed by spontaneous evaporation. 



No. 1. '365 grm. of salt, on drying in water-oven at 100°C, after 

 first well drving the powdered salt with blotting-paper, lost *1 70 grm. 

 = 46-57 per cent. OH 2 , = Na 2 S0 4 70H 2 . 



No. 2. -172grm. lost '031 grm. = 47*09 percent., = Na 2 S0 4 ,70H 2 . 

 No. 3. 2708 grms. lost l'273grm.=47'00percent., = Na 2 SO 4 ,7OH 2 . 

 No. 4. 1-260 grm. lost •605grm. = 47 > 00percent., = Na 2 SO 4 ,7OH 2 . 

 No.5.3-936grms.lostl-8l2grm. = 46-69percent., = Na 2 S0 4 ,70H 2 . 

 No. 6. 3-2/5 grms. lost 1-520 grm. = 46-4 1 per cent., = Na 2 S0 4 , 70H 2 . 

 No. 7.3-326grms.lostl-570grm.=47'llpercent., = Na 2 SO 4 ,7OH 2 . 



Weight. Loss. ■ OH 2 . 



No. grms. grm. per cent. 



1 -365 -1/0 = 46-57 



2 -172 -081 = 47-09 



3 2-708 1-273 = 47'00 



4 1-260 -605 = 47-00 



5 3-936 1-812 = 46-69 



6 3-275 1-520 = 4641 



7 3-326 1-570 = 47'11 



I trust that by the above-mentioned results I have clearly proved 

 the following facts with respect to supersaturated solutions of sodic 

 sulphate : — 



1 . That liquids and solids, such as alcohol, quicklime, &c, do 

 not determine crystallization by removing water. 



2. That thin films, when sufficient precautions are taken to guard 

 against the entrance of nuclei, do not act as nuclei. 



3. That chemically clean crystals of the normal salt (Na 2 S0 4 , 

 10H 2 O) do act as nuclei and are most powerful. 



4. That crystals of the normal salt are not produced in super- 

 saturated solutions of sodic sulphate on allowing it to evaporate 

 spontaneously, but that crystals of the modified (and known inactive) 

 salt are. 



In conclusion I may perhaps be permitted to state that the above 

 series of experiments have extended over a period of three years, 

 less a few months, and that most of them have been repeated a count- 

 less number of times, and with every conceivable modification and 

 check. Some few of them have already been published in the 'Che- 

 mical News,' but are here referred to again for the sake of compre- 

 hensiveness. 



