Manchester Memoirs, Vol. xli. (1897), No. 8. 11 



anything like so rapidly as these stronger ones, but still 

 much more rapidly than a mixture of potassium iodide 

 and iodate. I still consider, with Schonbein, that the 

 immediate evolution of oxygen with hydrogen peroxide 

 is a valuable indication that these solutions contain 

 hypoiodites. 



Lunge and Schoch prepared their " hypoiodite of 

 calcium " by rubbing together for some time iodine with 

 a large excess of lime and a comparatively small amount 

 of water, allowing to stand for some hours, and then 

 diluting with water. They thus obtained a solution 

 which apparently resembled Schonbein's solutions in 

 many respects, but gave " with cobaltous nitrate a green 

 precipitate — no black peroxide.'" It bleached cochineal, 

 logwood, and indigo carmine just as Schonbein's solu- 

 tions do. 



The authors attempted to estimate the bleaching 

 strength of the solution by means of a standard solution 

 of indigo carmine, standardised against a dilute solution 

 of bleaching powder, the strength of which was estimated 

 by means of a standard solution of sodium arsenite. 

 But they could not succeed in measuring the bleaching 

 power of their iodine-lime solution directly, because 

 towards the end the decolorisation was so extraordinarily 

 slow. They therefore added an excess of indigo solution, 

 and allowed to stand for 15 minutes ; then excess of 

 bleaching powder solution was added, and this excess 

 finally brought back by a drop or two of sodium arsenite 

 solution. In this way they estimated that in their 

 solution 14*6 per cent, of the total iodine present existed 

 as "bleaching iodine." They further stated that the 

 solution, kept in the dark, gradually lost its bleaching 

 power, but that only 76 per cent, of the bleaching action 

 had disappeared at the end of 23 days. They also tried 

 the effect of heating the solution, and found, on one 



