Chemistry and Physios. 449 



SCIENTIFIC INTELLIGENCE 



I. Chemistry and Physics. 



1. Determination of Small Amounts of Iron in Copper 

 Alloys. — A coloriraetric method for this jjurpose has been worked 

 out by A. W. Gregory by making use of the well-known color 

 imparted to solutions of ferric salts by salicylic acid. Two 

 tenths of a gram of alloy are dissolved in a minimum quantity 

 .of strong nitric acid. If a precipitate is formed, due to tin or 

 antimony, the liquid is diluted slightly and filtered. Lead if 

 present must be removed as sulphate. To the solution 20 cc of a 

 concentrated solution of sodium acetate are added and 10 cc of a 

 10 per cent, solution of salicylic acid in glacial acetic acid. A 

 3 per cent solution of potassium cyanide is now added grad- 

 ually until the green color of the solution has disappeared and 

 the precipitate of copper cyanide has dissolved. The liquid, 

 which is red if iron is present, is made up to a definite volume, 

 and a measured portion, depending upon the strength of the 

 color, is transferred to a Nessler comparison tube. The color is 

 then matched in another Nessler tube by adding a standard 

 solution of ferric chloride to the same amounts of sodium acetate 

 and salicylic acid solutions. By this method it is possible to 

 detect as little as '00002 g. of iron in the presence of '2 g. of 

 copper. The test cannot be employed in the presence of consid- 

 erable amounts of bismuth. Test analyses gave very accurate 

 results with quantities of iron up to *2 per cent. — Jour. Chem. 

 Soc, xciii, 93. h. l. w. 



2. The Action of Carbonates upon Tetrathionates. — A. Gut- 

 mann, having previously shown that dilute caustic alkalies con- 

 vert a tetrathionate into thiosulphate and sulphite, as, for example, 



2Na 2 S 4 6 + 6NaOH=3Na 2 S 2 3 + 2Na 2 S0 3 + 3H 2 0, 



has observed the peculiar circumstance that carbonates and 

 ammonia do not act in the same way upon a tetrathionate, but 

 produce thiosulphate and sulphate as follows : 



4Na 2 S 4 6 + 5Na 2 C0 3 = 7Na 2 S 2 3 + 2Na 2 S0 4 + 5C0 2 . 



Similar results were obtained with potassium carbonate, lithium 

 carbonate, and ammonia. The reactions take place upon boiling, 

 and they were shown to be sharply quantitative. A peculiar 

 result was obtained when carbonates of calcium, strontium and 

 barium were allowed to act upon a tetrathionate, for in these 

 cases it appears that a new isomer of ordinary thiosulphates is 

 formed, for it does not react like the latter when boiled with 

 potassium cyanide. It was found further that sodium tetrathion- 

 ate when boiled alone with water gives the reaction 



Na 2 S 4 6 = Na 2 S0 4 + S0 2 + S 2 , 



