640 



) 



Jamie 



son — Polythionic Acids. 







Na 2 S 2 3 .5H 2 



ccKI0 3 Na 2 S 2 3 .5H 2 





No. 



taken 



used 



round 



Error. 



1 



•0847 



16-0 



0848 



+ '0001 



2 



•1008 



19*0 



■1007 



— -oooi 



3 



•0613 



11-6 



0614 



4- '0001 



4 



•0413 



7-8 



0413 



•oooo 



5 



•1145 



21-6 



1145 



•oooo 



6 



•1329 



25-1 



1330 



+ -oooi 



7 



•1554 



29*35 



1555 



+ -oooi 



8 



•1716 



32-4 



1717 



+ '0001 



9 



•2051 



38-7 



2051 



•oooo 



10 



•2430 



45-95 



2435 



4- -0005 



11 



•1923 



36'3 



1924 



4 '0001 



12 



•1936 



36-6 



1939 



4 '0003 



The results in both tables show a satisfactory agreement among 

 themselves and with the actual amounts present. 



A volumetric method for the determination of tetrathionic 

 acid has been described by E. Abel* which is based upon add- 

 ing an excess of standard iodine solution to the solution of the 

 tetrathionate which has been made strongly alkaline. Then 

 the solution is acidified with hydrochloric acid and the liberated 

 iodine is titrated with a standard solution of sodium thio- 

 sulphate in the usual manner. The iodate method has the 

 advantage in requiring only a single standard solution. h\ 

 order to test the method, sodium tetrathionate was prepared 

 according to the method of F. Kesslerf by grinding sodium 

 thiosulphate with a slight excess of iodine in the presence of a 

 few cubic centimeters of water. When the sodium thiosulphate 

 was entirely dissolved, two volumes of absolute alcohol were 

 added. After the solution had stood for two hours, the sodium 

 tetrathionate crystals were filtered by suction and washed with 

 98 per cent alcohol until all the iodine and sodium iodide were 

 removed. The sodium tetrathionate was found to contain 

 some sulphate which was determined by the following method. 

 Weighed portions of the salt were dissolved in water and 

 acidified with one gram of tartaric acid. Barium chloride was 

 added to the solution, and when the precipitate had settled, it 

 was filtered and determined in the usual manner. The follow- 

 ing results were obtained : 



I. -3225 g. Sub. gave -0181$ BaS0 4 = 3-31$ 

 of Na 2 S0 4 

 II. -3333 g. Sub. gave -0186$ BaS0 4 = 3-39$ 



of Na 2 S0 4 Average - 3-35$ of Na 2 S0 4 



Two water determinations were made at about 112° C. 



I. 1-0000 g. Sub. gave 11-27$ of water 

 II. 0-5000 g. " *' 11-37$ " " 



* Z. anorg. Ch. lxxiv, 395. 



Calc. water forNa 2 S 4 6 .2H 2 after 

 correction for 3 -35$ of Na 2 S0 4 . 

 11-35$ 



f Pogg. Ann. lxxiv, .255, 1848. 



