218 Scientific Intelligence. 
pure mercury in contact with air can no longer be doubted, The 
same is true of iron, zinc, cadmium, lead, copper and tin. Now 
thermic data explain this phenomenon. For each equivalent of 
oxygen fixed by the metal, iron (rust) evolves 31:9 calories; tin 
34°9; cadmium 33°2; zinc 41°8; lead 26-7; copper 21:0, and 
Silver, for example, evolves only 3°5 calories per equivalent of 
oxygen absorbed. The fact that a reaction begins spontaneously 
only in the case where a notable evolution of heat takes place, is 
a result not unfrequently observed; seeming as if there was a 
May, 1881. ; 
2. On Hesperidin, a Glucoside of the Aurantiacew.—TIEMANN 
peridin. It appears to be aniversally diffused through the family 
of the Aurantiacee and is most readily prepared from the dried, 
unripe officinal orange ructus aurantii immaturi). The 
lead acetate gave a precipitate in the extract. The residue was 
gn : 
r 
solution was no longer solored: From this last solution, mineral 
acids precipitate crude hesperidin. This is boiled with 90 per 
cent alcohol to remove coloring m Ss a 
solved in very dilute potash solution, and precipitated by & pati! 
current of carbon dioxide. It is well washed and dried. As thus 
*The symbols in these equations represent equivalents, not atoms. 
