CHEMICAL SCIENCE. 265 



ing nearly to diyness, and diluting to 10,000 grains measures with 

 distilled water at 60 ; and from this, other standard solutions of 

 different strengths Avere formed. A convenient quantity of the water, 

 generally half a gallon, was evaporated to dryness, and the saline 

 mass so obtained was afterwards dissolved in hydrochloric acid. The 

 iron contained in the solution having been converted into perchloride 

 by boiling with a few drops of nitric acid, the silica and other insolu- 

 ble substances were separated by filtration, and the peroxide of iron 

 precipitated by ammonia. This latter precipitate was collected on a 

 filter, and well washed with water. It was then re-dissolved in the 

 smallest possible quantity of hydrochloric acid, and the liquid having 

 been introduced into a phial or tube of known capacity was diluted 

 with distilled water, until it reached a particular mark upon the side, 

 corresponding to 1000 water-grain measures ; care being taken of 

 course to add previously a few drops of a solution of sulphocyanide 

 of potassium. The depth of tint was then compared with that of the 

 standard solutions before mentioned, contained in tubes or phials of' 

 similar diameter, in which certain known quantities of iron, ranging 

 from the y^g-o to the 7 of a grain, were contained in the same bulk of 

 water. In order to render the comparison of tints more perfect, the 

 tubes were placed against a sheet of white writing paper, and held 

 between the eye and the diffused light. Operating in this way, the 

 author was enabled to estimate the -^TO ^ a g ra i n f ^ ron P er gallon 

 with the greatest readiness. It was sometimes found preferable to 

 employ but one standard solution. The proportion of iron, in the 

 liquid tested, was then determined by measuring the volume of water 

 that was required to lighten the tint so as to render it identical with 

 that of the normal solution, or vice versa. Quarterly Jour. Chem. Soc. 



r 



SEPARATION OF MANGANESE. 



Dr. Schell, of St. Louis, recommends the following method for the 

 separation of manganese : If a current of chlorine is passed through 

 a diluted solution of acetate of manganese, or better, through a mix- 

 ture of chlorid of manganese and acetate of soda, the acetate of man- 

 ganese is decomposed after a very short time and all the manganese 

 precipitated as peroxyde, while the acetates of iron and of nickel are 

 not affected under similar circumstances. Therefore, if a solution of 

 chlorides of manganese, nickel and iron contains free hydrochloric acid, 

 a sufficient quantity of acetate of soda is added to convert all the 

 chlorides into acetates and bind the free hydrochloric acid. The free 

 acetic acid thus liberated does not prevent the formation of peroxyde 

 of manganese. By this method, cobalt cannot be separated from 

 manganese, because it is also partly precipitated. 



ON A NEW TEST FOR UREA. 



As is well known, a dilute aqueous solution of corrosive sublimate 

 may be mixed with an excess of a solution of bicarbonate of potash 



