Chemistry and Physics. 215 



plant is 3| tons of ore per day and the operations have been emi- 

 nently successful. Up to October 10, 1915, nearly 5 grams of 

 radium, calculated as element, had been extracted and about 2-|g. 

 of this had been delivered to the hospitals in the form of radium 

 bromide. The market price of radium for two or three years has 

 been $120,000 or more per gram, and it is estimated that the cost 

 of the radium produced at the works in Denver has averaged 

 137,599 per gram. The method of extraction that has been used 

 is novel in some respects, particularly in the employment of nitric 

 acid for the initial treatment of the ore. The radium is almost 

 completely dissolved by this treatment along with nearly all of 

 the uranium and a large part of the vanadium. In the course of 

 the operations for separating and recovering the radium, uranium 

 and vanadium, the nitric acid is finally converted into sodium 

 nitrate, and from this the nitric acid is recovered, so that there is 

 little loss of this reagent. From the nitric acid solution of the 

 ore the radium is precipitated along with barium sulphate by the 

 addition of a barium salt and sulphuric acid. The barium-radium 

 sulphates are then reduced to sulphides by ignition with carbon, 

 the sulphides are converted into chlorides by means of hydro- 

 chloric acid and then the chlorides, -and afterwards the bromides, 

 are separated by fractional crystallization. After the removal of 

 the radium from the nitric acid solution an excess of sodium car- 

 bonate is added to precipitate iron and calcium; then, after the 

 removal of the precipitate, sodium uranate containing some vana- 

 dium is precipitated by means of sodium hydroxide, and finally iron 

 vanadate is precipitated by means of ferrous sulphate. The car- 

 notite ore used averaged 2*66 per cent of U 3 8 and about Of milli- 

 grams of radium per ton, which is about 1 part in 200,000,000. The 

 publication contains very full details of the operations and includes 

 many illustrations showing the buildings and the apparatus 

 employed. — U. S. Bureau of Mines, Bulletin lOJf.. h. l. w. 



2. The Qualitative Separation of Silver from Univalent Mer- 

 cury. — N. von Zweigbeegk has studied the method which is 

 generally used by students in detecting silver chloride in the 

 presence of mercurous chloride, and which consists in treating 

 mixtures of the two chlorides with ammonia. It has been known 

 for a long time that the method is unreliable when the amount of 

 silver chloride present is small in comparison to the mercurous 

 chloride, and the investigation under consideration has confirmed 

 this fact. It appears that the reaction of mercurous chloride with 

 ammonia is represented by the equation : 



2HgCl + 2NH 3 = HgNH 2 Cl + Hg, 



and that the ammoniacal silver chloride solution reacts with the 

 metallic mercury somewhat irregularly, being affected by mass 

 action, as follows : 



2 AgCl(NH,) s + Hg = HgNH 2 Cl + NH 4 C1 + 2NH 3 + 2Ag. 



Some quantitative experiments gave the following interesting 

 results, where double-normal ammonia was used for the reaction, 



