Chemistry and Physics. 381 



2. On the direct union of Bromine with Chlorides, forming a 

 ■new class of Perbromides. — In a series of experiments upon the 

 reaction which takes place between bromine and certain chlo- 

 rides, Berthelot has observed the formation of a new group of 

 secondary compounds produced by the direct addition of bro- 

 mine to these chlorides, in strict analogy to the formation of the 

 alkali perbromides. When for example fuming hydrogen chlo- 

 ride, of specific density V153, is mixed with bromine, 100 c. c. 

 dissolve within a few minutes 36*4 grams of the bromine; in- 

 creasing finally to 40'1 grams. The ratio between the two is 36*5 

 to 40* I ; which corresponds to the formula (HCl) 2 Br. This fact, 

 as well as the calorimetrical one that the heat evolved in the 

 reaction is double that evolved when bromine is dissolved in 

 water, proves, in the author's opinion, the formation by direct 

 union of a bromide of hydrogen chloride, comparable to hydro- 

 gen perchloride. Analysis showed that at most only one three- 

 hundredth of one equivalent of the chlorine had been replaced. 

 This fact as well as the ready dissociation of the compound 

 shows that the bromine has acted by direct union and not by 

 substitution. Hydrogen chloride dissolves iodine also in much 

 larger proportion than water, one liter dissolving 6*04 grams; 

 thus indicating the formation of a similar periodide. A solution 

 of barium chloride containing 450 grams of the crystallized salt 

 to the liter dissolves 1 1 5 grams bromine, nearly four times the 

 quantity dissolved by the same quantity of pure water. The 

 heat evolved is 0*5 calory for Br liquid = 80 grams. The solu- 

 tion may be diluted with its own volume of water without throw- 

 ing down the bromine. Only one hundredth of an equivalent of 

 the chlorine suffered replacement in this experiment. A solution 

 of strontium chloride containing 400 grams of the crystallized 

 salt to the liter, dissolves 92 grams of bromine, three times as 

 much as pure water. The same kind of absorption has been ob- 

 served with silver chloride. — Bull. Soc. Ch., II, xliii, 545, June, 



1885. G. F. B. 



3. On the Reduction of Carbon dioxide to monoxide by Carbon. 

 Natjmann and Pistor have studied the conditions, especially of 

 temperature, under which carbon dioxide is reduced to monoxide 

 through the action of carbon upon it. In the first five experi- 

 ments (which were conducted at comparatively low temperatures 

 in order to determine the lower limit at which the reduction took 

 place) a combustion tube 82 cm. long and 15 mm. in diameter, was 

 used, filled with fragments of charcoal previously washed with 

 acid and then strongly ignited. Through this tube the carbon 

 dioxide, prepared from marble and hydrogen chloride and care- 

 fully dried, was passed at the rate of 2 or 3 bubbles per second ; 

 the tube being heated in a gas furnace, and being surrounded 

 with two concentric sheet iron tubes enclosing wire spirals, for 

 the purpose of rendering the temperature more uniform. In 

 order to measure the temperature, a number of capsules of glass 

 -or platinum, containing salts of different melting points and for 



