196 ANNUAL EECORD OF SCIENCE AND INDUSTRY. 



temperatures. Whenever a crystalline salt is dissolved in 

 water and the solution frozen, solidification takes place heloio 

 the Centigrade zero, and a definite compound of the water 

 with the salt is formed. And whenever any crystalline salt 

 is mixed with ice or snow, the same compound is formed, 

 and a fall of temperature ensues. Hence with every crystalline 

 salt a freezing mixture may be prepared. Guthrie now ex- 

 tends his observations to colloid bodies, and shows that they 

 act very difierently from the crystalloids. Thus from a solu- 

 tion of gum, gelatin, or albumen all the water separates as ice 

 at Centigrade, and no cryohydrate is produced. This new 

 distinction between crystalloids and colloids seems to be of 

 the very highest importance. 1 A^June 30. 



NATUEAL DEVELOPMENT OF SULPHUEETTED HTDEOGEN. 



Faulquier narrates a curious phenomenon which took place 

 during the summer of 1875 at Palavas, near Montpellier. 

 In the vicinity of this place are extensive salt marshes, 

 which, in consequence of persistent north winds, have become 

 almost dried up. The accompanying heat of the season has 

 produced a rapid decomposition of the organic matter in the 

 soil, which has been accompanied by a development of sul- 

 phuretted hydrogen. The existence of this gas has been 

 very palpable to the senses, and lias also produced an unex- 

 pected influence upon the residences near by, the painted 

 surfaces of the houses having first turned brown, and finally 

 almost entirely black, while the paint even in the interior of 

 the houses has become much altered. All silver and silvered 

 objects have also become blackened by the same influences. 

 Another efiect is that of loosening and crumbling away of 

 the plaster between the joints of the building-stones, which 

 Faulquier attributes not to the sulphuretted hydrogen, but 

 to the saline particles contained in the atmosphere. 1 -Z?, 

 September 5, 346. 



AMMONIA IN SULPHUEIC ACID. 



Professor F. H. Storer finds that ammonia in traces is an 

 invariable contaminant of sulphuric acid. Nine samples of 

 acid were examined from difl'erent manufactories, seven beinc: 

 obtained direct from the makers. These w^ere kept j^revious 

 to examination in tightly stoppered bottles, and in every case 



