198 ANNUAL OF SCIENTIFIC DISCOVERY. 



to allow of the slightest communication with the platinum tube, which 

 was filled with dry air. On exposing this tube to a high temperature, 

 the air by degrees lost its oxygen, and water was formed ; a circum- 

 stance which could only be explained by admitting that hydrogen had 

 penetrated through the pores of the platinum tube ; and, on the tem- 

 perature being further raised, a considerable quantity of free hydrogen 

 was found to issue from that tube. This shows that platinum, at a 

 high temperature, is capable of producing the phenomena of endos- 

 mosis with gases. 



CONCENTRATION OF MINERAL WATERS. 



Sea-water, in freezing, forms flakes of ice consisting of nearly pure 

 water, and an extremely saline liquid which in northern countries is 

 utilized in the production of marine salt. Very recently, Dr. Robinet, 

 a physician of Pacis, has discovered that the same process can be ap- 

 plied in the purification of fresh water. In freezing water from the 

 Seine, from wells, and from springs, he found the ice produced to be so 

 entirely free from the salts of lime and magnesia which were contained 

 in the water, that, thus purified, it may be considered as nearly equal 

 to distilled water. So it is now proposed to procure water on board 

 ships, no longer by distillation but by congelation. 



The same fact is made use of in the concentration of mineral waters, 

 a problem which has offered itself for a long time, but which the em- 

 ployment of heat could not solve, on account of the gas originally in 

 solution which the heat expelled. Cold works better. Dr. Ossian 

 Henry, of Paris, has experimented with forty different varieties of 

 water, and finds that it is possible, by congelation, to reduce mineral 

 waters to one-eighth, one-tenth, one-fifteenth, or even one-twentieth of 

 their original volume, without producing any alteration in the gases 

 contained in them. 100 litres of mineral water can thus be reduced to 

 5, giving great economy to transportation ; moreover, the ice itself is 

 also valuable. But we do not believe that the therapeutic properties 

 of the extract will be identical with those of the water in its original 

 state, because of the changes which manifestly take place in the con- 

 tained salts, changes so evident that Mr. Balard has been able to base 

 upon them a manufacture of sulphate of soda, by exposing to a tem- 

 perature sufficiently low the water containing NaCl and MgO, SO 3 , 

 which result from the manufacture of sea-salt by the evaporation of 

 sea-water. 



The publication of this process has given occasion for a protest on 

 the part of Mr. Tichon, an apothecary of Aix les Bains (Savoy), ac- 

 cording to which the same process has been used since 185G, by him 

 and a Mr. Melsens, who was staying at Aix for his health. The min- 

 eral water which he drank here, and which is sulphurous, proving dis- 

 agreeable to his taste, he undertook to remove part of the odor by sub- 

 mitting it to a freezing mixture. In this way, he was able, not only to 

 mask the disagreeable odor, but also to concentrate the mineral in- 

 gredients. Mr. Tichon adds that congelation will not suit all mineral 

 waters, inasmuch as it alters the organic matter therein dissolved. 



