Chemistry and Physics. 125 
ming muriatic acid added in small portions at a time, a snow-white pre- 
cipitate of pure ferrocyanhydric acid is thrown down. These are to be 
washed with muriatic acid, dried upon a brick, and dissolved in alco- 
hol; from the alcoholic solution the acid may be obtained in beautiful 
crystals.-Ann. der Chemie und Pharmacie, \xxxvii 
lt remains in solution as unaltered double cya he sesqvioxyd 
of nickel may be washed and ignited, and the nickel weighed in the 
form of protoxyd ; it is perfectly free from cobalt. ‘The solution after 
and treated with chlorine. ‘This method of separating cobalt and nick- 
el has perhaps some advantages over Liebig’s second method which, it 
will be remembered, consists in boiling the mixed double cyanids with 
oxyd of mercury, which precipitates the nickel but not the cobalt. 
1 na general method of volumetric analysis.—-BuUNSEN has giv- 
€n a very accurate and elegant method for the volumetric determina- 
tion of a great number of substances. The principle of the method 
he chlorine is to be ¢ ed int solution of iodid of potassium, 
and the evolved iodine volumetrically determined by means of a 
tion of sulphurous acid. ose in which a substance is sus- 
By calculation. By analysis. 
Fe2QOs . . 68-97 68-96 
FeO... . 31-03 31:04 
100-00 ; 100-00 
