74 J. Bhaduri — Transformation of [No. 2, 



sium iodide. Alkaline solutions on the other hand remain perfectly 

 unaltered in a boiling solution of a chlorate. In this respect the be- 

 haviour of potassium iodide as to liberation of iodine is exactly similar 

 to the oxidation of arsenious oxide (arsenites) to arsenic oxide (arseni- 

 ates). Arsenites in alkaline solution are readily oxidised by hypochlo- 

 rites, but are without any action upon chlorates. Hence only Penot's 

 method was found applicable. The solution which had been used being 

 strongly alkaline owing to the pi-esence of free sodic hydrate, separation 

 of the latter was necessary before potassium iodide could be added. 

 This was attempted to prevent the spotting operation in Penot's process. 

 Direct estimation however proved abortive. Mercuric chloride, copper 

 sulphate, &c, were used to separate the alkali in the form of insoluble 

 hydrates or oxides, but part of the hypochlorite seemed to be decom- 

 posed precipitating oxychlorides. When magnesium sulphate was used, 

 magnesium hydrate was precipitated, but on subsequent addition of 

 potassium iodide, the liberated iodine combined with the hydrate, ren- 

 dering the process useless. 



Action of chlorine on sodic hydrate. 

 Preparation of sodic hypochlorite: 

 The hypochlorite was made by passing washed chlorine through a 

 solution of sodic hydrate made from metallic sodium. Its strength in 

 different experiments varied from l - 5 to 25 °/ . The temperature at 

 which absorption took place also varied from 25° C. to 33° C. and the 

 passage of the gas continued in some experiments for four to five hours. 

 The solution in dilute condition was colourless, but had a greenisb 

 yellow colour in a more concentrated form. It had a distinct and 

 peculiar smell unlike chlorine. This was so characteristic that the 

 intensity of odour gave an appoximate idea of the strength of hypochlo- 

 rite present in a solution. Though the solution was strongly alkaline 

 owing to the presence of free alkali, yet immediate liberation of iodine 

 from a solution of potassium iodide took place. The solution instantly 

 turned the brilliant surface of mercury yellowish red, oxychloride of mer- 

 cury being produced. In connection with this it was further observed 

 that the colour changed in the course of few hours from greenisb yellow 

 to purple, even when kept in the dark. This was due to the powerful 

 oxidising and solvent action of hypochlorites in alkaline solution. The 

 manganous silicate contained in the glass was oxidised, even in the 

 strongly alkaline solution, and in presence of a chloride, and converted 

 into sodium permanganate. A solution of sodic hydrate however did 

 not under like conditions turn purple. As these experiments were 

 performed in the dark room, the transformation (see pp. 76-79), had 

 there been any, must have been insignificant. 



