TRANSACTIONS OF SECTION B. 563 



vary largely with each sample, as is to be expected ; indeed, so largely did they 

 diverge from one another, that no definite percentage could be given as likely to 

 exist in a partially washed sample of bleaching powder. The samples which were 

 examined in this investigation ranged between 22 and 30 per cent. The percentage 

 of residue in the completely washed samples did not show such a large variation. 

 In the particidar samples, the percentage of chlorine in which is given above, there 

 was found in the English sample 8-1 per cent, residue, in the Swiss sample 7'9 per 

 cent. And an examination of various samples of bleaching powder of different 

 strengths showed that the percentage only varied between 7 per cent, and 9 per 

 cent. 



The remaining part of this investigation presented many difficulties. The residue, 

 which had failed to give a reaction with the iodine and starch solution, together 

 with acetic acid, when dried, certainly did evolve, on the addition of a few drops of 

 hydrochloric or sulphuric acid, a most minute quantity of a bodj' which slightly 

 acted on wet iodine and starch paper ; but so small was the quantity of this body 

 which could be obtained, though several pounds of residue were experimented with, 

 that no correct idea of its nature could be formed ; but the results of the numerous 

 experiments made with it went to prove that it is not a basic clilorate, as stated by 

 Persoz, but simply a trace of a soluble hypochlorite which escaped being removed 

 from the residue by washing. 



Many attempts were made to estimate, m the completely washed residue, this 

 trace of a bleaching agent, in a manner similar to that adopted for its estimation in 

 the partially washed residue, but without success. 



As to Persozs statement that, when the residue is completely deprived of its 

 bleachuig power, and then spread over woven fabrics in such a manner as to find 

 its way into their interstices, if the fabrics be then submitted to a bath of hydro- 

 chloric acid, so energetic is the gas evolved from this supposed basic chlorate, that 

 the fabrics are burnt into holes in many places ; — this statement, so far as these 

 experiments go, is certainly without foundation, though the residue was tortured 

 in every conceivable manner in the endeavour to detect in it anj' body capable of 

 injuring textile fabrics. Among the experiments made with it, the following are 

 a few : — 



1st. A certain weight of the residue was mixed with just sufficient water to 

 allow it to penetrate through the fabric being experimented with ; this mixture 

 was then pasted on one end of a piece of fine unbleached cotton. The same weight 

 of a mixture of lime and carbonate of lime as of the residue was mixed with the 

 same quantity of water, and then pasted on the other end of the piece of cotton. 

 The cotton was now set aside until the residue and lime mixture had dried on it, 

 after which, by means of a fine dropping tube, the same quantity of a normal hj'dro- 

 chloric acid solution was pom-ed over the residue and lime mixture, and when all 

 effervescence had ceased, a few drops more acid were added, and the piece of cotton 

 allowed to rest for some time, after which it was washed ; and on examination the 

 result was found to be the same with the lime as with the residue — both ends of 

 the cotton were slightly yellow, but in no way bleached or damaged. 



This experiment was repeated many times in various ways, and with a variety 

 of fabrics, such as unbleached linen, blenched linen, calico, and cotton printed with 

 fugitive colours ; but though the unbleached linen and cotton were boiled in a solu- 

 tion of tlie residue, and then passed through an acid bath, no more effect could be 

 perceived than when a piece of the same goods was boiled in a solution of the same 

 quantity of the mixture of Ihue and carbonate of lime, and then passed through the 

 acid bath. In case it might be considered that boiling had a neutralising eflect oa 

 any basic chlorate existing in the residue, various pieces of different fabrics were 

 allowed to steep in a solution of the residue for over a week, and then placed for 

 several hours in an acid bath, without being in the least degree injured. "When 

 the fugitive colour on the printed calico was not altered by lime, neither was it 

 affected by the bleachmg powder residue. In order to correctly investigate the 

 remaining question, queries were addressed to several of the best known proprietors 

 of Irish linen bleach-greens, as to the exact method adopted by them for the manu- 

 facture of the hypochlorite of lime solution, and also the quantity of water used to 



2 



