76 ' J. Bliaduri — Transformation of [No. 2, 



In order to study the action of chlorine on a solution of sodic 

 hy-drate, a certain volume of freshly prepared solution of sodium hypo- 

 chlorite, prepared as before, was reduced either by zinc copper couple 

 or alkaline ferrous hydrate, and the total chlorine estimated volume- 

 trically by standard silver nitrate. The hypochlorite and cblorate were 

 then estimated separately as detailed in previous sections. The per- 

 centage of alkali was estimated by (i) titration with semi-normal hydro- 

 chloric acid (before passing chlorine), and (ii) converting into anhydrous 

 sodium sulphate and weighing as such. These experiments were re- 

 peated at least twice with the same solution. On page 75 the results 

 of analyses (about fifty) are given in a tabular form. Results from 

 columns (d) and (e) — available chlorine of hypochlorite and chlorate, 

 have been added, and put in (/), side by side with (gf) which represents 

 the total chlorine. 



Solutions from iii. to ix. all turned purple when kept in litre flasks. 

 The colour was due to the formation of permanganate, the glass of the 

 vessels used furnishing the manganese. The last five sets of experi- 

 ments were performed at temperatures which were decidedly lower 

 (some 5° C) than the temperatures of the first four sets of experi- 

 ments. It is clear from the above table that the amount of chlorate 

 which is formed in solution up to 7 °/q of concentration (free NaOH) 

 is insignificant, and hence the following equation represents under 

 the above mentioned circumstances the action of chlorine on sodium 

 hydrate : — 



2 NaOH-fCl2 = N'aOCl-fNaCl + HOH. 



Above 10 °/q concentration, the secondary reaction — transformation 

 — becomes more distinct, and when the concentration exceeds 20 %, time 

 becomes an important factor in bringing about the change. In the 

 course of one series of experiments such a solution which was kept in 

 the dark showed a change of only 6 % in twenty-four hours. "When, 

 however, chlorine was passed for about an hour the change in another 

 part of the same solution amounted to 1'5 °/o. Evidently then the 

 presence of free alkali retards the transformation. This fact will be 

 noticed in the next section, dealing with the transformation in the dark. 



Transformation of the cold solution in the dark. 



Temperature 25-28°G. 



A number of tubes containing definite volumes of hypochlorite 

 solution of known strength was sealed and kept in closed drawers in the 

 photographic room of the laboratory in which sometimes yellow and 



