Gooch and Osborne — Potassium Aluminium Sulphate. 169 



the precipitate due perhaps to the prolonged treatment in glass. 

 As will appear, however, the process of hydrolysis did not go 

 to the point of forming aluminium hydroxide. 



The degree to which the acidic ion is removed hydrolytically 

 from the salt under. the conditions is shown in the following 

 series of experiments in which portions of the alum were 

 treated with the bromide-bromate mixture under conditions 

 which permitted the collection and titration of the bromine set 

 free in the reaction. 



The apparatus used consisted of a Yoit flask, used as a distil- 

 ling flask, sealed to the inlet tube of a Drechsel wash bottle, 

 used as a recei ver, to the exit tube of which was sealed a Will and 

 Yarrentrapp absorption tube. The Yoit flask was charged with 

 0'5 grm. of alum dissolved in a little water and 25 om3 or 30 cm3 

 of the bromide-bromate mixture. The solution was boiled foi 

 the time indicated and the bromine liberated passed in a cur- 

 rent of hydrogen, sent through the whole apparatus, to the 

 receiver containing in the cylinder and trap a solution of 

 4 grm. of potassium iodide in *200 cra3 of water. The iodine set 

 free by the action of the bromine liberated in the reaction was 



titrated by 

 indicator. 



10 



sodium thiosulphate with the aid of a starch 



Table II. 



Theory 6Br to 2KA1(S0 4 ) 3 .12H 2 0. 



KAl(SO t ) 2 .12H 2 

 Time taken 



KBr 



used 



KBr0 3 



used 



Bromine 

 liberated 



Theory for 

 bromine 



Error in 

 terms of 

 bromine 



Error in 



terms of 



A1 2 3 



hrs. grm. 



grm. 



grm. 



grm. 



grm. 



grm. 



grm. 



0-5 0-5000 



1-8 



0-5 



0-2052 



0-2527 



0-0475 — 



o-oioi— 



1-5 0*5000 



2-16 



0-6 



0-2064 



0-2527 



0*0463— 



0-0097— 



2-0 0-5000 



2-16 



0-6 



0-2084 



0-2527 



0-0443— 



0-0094— 



2-5 0-5000 



2-16 



0-6 



0-2099 



0-2527 



0-0408— 



0-0091— 



3-5 0-5000 



2-16 



0-6 



0-2119 



0-2527 



0-0408— 



0-0087 — 



4- 0-5000 



2-16 



0-6 



0-2120 



0-2527 



0-0407— 



0-0086— 



B 

 Theory 5Br to 2KA1(S0 4 )2.12H 2 0. 



0-5 



0-5000 



1-8 



0-5 



0-2052 



02106 



0-0054— 



0-0011 — 



1-5 



0-5000 



2-16 



0-6 



0-2064 



0-2106 



0-0042 — 



0-0009 — 



2-0 



0-5000 



2-16 



0-6 



0-2084 



0-2106 



0-0022— 



0-0005 — 



2-5 



0-5000 



2-16 



0-6 



0-2099 



0-2106 



0-0007 — 



o-oooi — 



3-5 



0-5000 



2-16 



0-6 



0-2119 



0-2106 



0-0011 + 



0-0002 + 



4-0 



0-5000 



2-16 



0-6 



0-2120 



0-2106 



0-0014 + 



0-0003 + 



