TKANSACTIONS OF SECTION B. 561 



the 'bleacliing of mixslin. Persoz does not agree witli M. Edouard Schwartz, that 

 tliis damage to the goods, perceived hy the former, arises from small hubbies of 

 chlorine gas, as he determined by direct experiment that muslin in a wet condition 

 could be submitted to chlorine gas for a considerable period without imdergoing 

 sensible alteration ; but he believed that there existed in the insoluble portion of 

 the bleaching powder of commerce a basic compound of imknown composition, and 

 that to this compound the destruction of the fibre was due. In proof of this, he 

 mentions that on washing a sample of bleaching powder till he could no longer 

 detect any bleaching agent, he obtained a residue containing more or less lime and 

 carbonate of lime, and on the addition of hydrochloric acid to this residue there 

 was evolved a most energetic oxidising agent. He also relates that, on spreading 

 this residue on woven fabrics, and afterwards passing these fabrics through an acid 

 solution, holes were produced in them in many places. Now, as these statements 

 of Persoz are considered correct by many eminent chemists, though they have, as 

 far as could be ascertained, not been veriBed, and as they are, if correct, of serious 

 importance to the bleacher. Professor Lunge suggested the advisability of submit- 

 ting the matter to careful investigation, and with that object a series of experiments 

 was undertaken, the results of which are here described : — 



The investigation was divided into several parts. 



(1 .) Coidd bleaching powder be deprived by washing with cold or tepid water 

 of its power to act on iodine and starch paper ; and if so, how much water is 

 required for a definite weight of powder ? 



(2.) What is the percentage of residue after the complete extraction of the 

 bleaching agent ? 



(3.) If the residue in which iodine and starch paper failed to detect any bleach- 

 ing agent would evolve any oxidising body on the addition of an acid ? 



(4.) What is the effect of the residue with the addition of an acid on textile 

 fabrics ? 



(5.) ^Vhat is the percentage of chlorine left in the residue of bleaching powder 

 which has been dissolved for the preparation of a bleaching solution by Irish 

 bleachers, and what effect has this residue with and without an acid on 

 fabrics ? 



The apparatus employed for the solution of the first question were merely (1st), 

 glass funnels, into which fitted small cones of De La Rue's parchment paper, over' 

 which were placed cones of Swedish filter paper ; the funnels were now attached^ 

 to Bunsen's filter pump bottles, and the filter paper allowed to become thoroughly 

 dry ; (2nd) newly-prepared iodine and starch paper. 



Three samples of bleaching powder having been reduced to a uniform degree of 

 fineness were examined for the percentage of chlorine, vnth the following results : — 



1st. English bleach . . . contained 35-399 per cent, chlorine. 

 2nd. Swiss „ „ 35-760 „ „ 



3rd. Specimen prepared ua laboratory „ 43-180 „ „ 



The sample No. 3, which contained such a high percentage of chlorine, was pre- 

 pared by a student of Professor Lunge's, and an account of its manufactui-e will, I 

 believe, after some time be published. 



Having weighed carefully 10 gi-ammes of each sample, they were placed in the 

 funnels, and 100 c.c. of distilled water, at 15° C, was poured over each. The pumps 

 were then set in action, and when all the water had completely passed through, 

 each filtrate was examined for chlorine by Penot's arsenious acid process, after 

 which the filter bottles, having been thoroughly washed and dried, another 100 c.c. 

 of distilled water was added to each 10 grammes, and the pumps again set in action. 

 This operation was repeated until each sample had been washed with 600 c.c. of 

 distilled water, and though the filtrates still gave a most decided reaction with the 

 iodine and starch paper, almost all the chlorine had been washed out, as can be 

 seen by the following table : — 



1880. 



