ON THE ATOMIC WEIGHT OF CHLORINE. 183 



of the 2-litre flask was determined. It was assumed that no loss in weight of the 

 iodine had occurred during its solution in the potassium iodide solution. We had 

 then 28'58332 grammes of iodine dissoved in 2033'68 of our units of volume, which 

 gives '014055 gramme of iodine in one of our units of volumes. The solution was 

 kept in the tightly stoppered 2 -litre flask. 



Potassium Hydrate. Potassium hydrogen carbonate was twice re-crystallised from 

 water. The crystals were heated in a platinum crucible, fitted with a platinum hood, 

 to a dull red heat for six hours. The potassium carbonate so obtained was dissolved 

 in water, and silver carbonate added, and the mixture thoroughly agitated for 

 three hours. The precipitate, composed chiefly of silver carbonate but probably 

 containing traces of silver chloride and other substances, was allowed to settle and 

 the supernatant liquid filtered into a silver dish through a filter filled with clean 

 pieces of broken marble. 



The solution in the silver dish contained one part of potassium carbonate in twelve 

 of water. It was heated to the boiling-point, and two parts of lime (prepared by 

 heating calcium carbonate to bright redness in a platinum crucible, and previously 

 slaked in ten parts of water) were added by degrees, the liquid being boiled for a few 

 minutes after each addition of lime to ensure its complete conversion into calcium 

 carbonate. The addition of lime completed, the solution was boiled for half-an-hour 

 and allowed to clarify by standing. The clarified solution was then filtered through 

 another marble filter into a silver dish and boiled down until the hydrate commenced 

 to evaporate. The semi-solid mass was then poured into a silver dish and allowed to 

 cool in vaauo over calcium chloride. It was then divided into four portions, the first 

 was broken into small fragments and introduced as rapidly as possible into the potash 

 drying tubes ; the second was broken into larger pieces with which the chlorine 

 absorption tube (fig. 3) was filled ; the third was dissolved in pure distilled water 

 and the solution employed in the preparation of potassium iodide, whilst the remainder 

 was used in the purification of water. 



Pure Water. The water used in these experiments was prepared by rectifying hot 

 distilled water from the laboratory still. This was distilled over potassium hydrate 

 (purified as described) and potassium' permanganate, twice re-crystallised from water. 

 The retort employed was made of hard Bohemian glass, the condensing tube and 

 receiver of Gerate glass. Immediately before use these were cleaned and steamed. 

 100 cub. centims. of this water, when slowly evaporated in a small platinum retort, 

 gave no solid residue. 



Phosphorus Pentoxide. KAHLBAUM'S purest pentoxide, contained in Jena hard 

 glass tubes, was distilled, at a bright red heat, in a current of pure dry oxygen 

 through spongy platinum, kept in position by two platinised asbestos plugs. The 

 distilled oxide condensed as a fine white crystalline powder in the cooler part of the 

 Jena-glass tubes. It was kept in a tightly stoppered bottle until its introduction 

 into the drying tubes. It answered all the tests recommended by SHENSTONE and 



