B!r:tcllillg. 



Soap. 



Oxymuria- 

 -lic acid. 



532 



Alkali. 

 Crystallised carbonate of potash, 41 

 Ditto carbonate of soda, . ... 21^ 

 Ditto ditto desiccated, 60 



Hence it appears evident, of what importance it is 

 to bleacher?, and others who use alkalis in any quan- 

 tity, to have it in their power to ascertain the quan- 

 tity of pure salt contained in them ; as, by a proper 

 knowledge of this, great saving may be made by 

 them in the course of their business. 



III. Soap is an article so well known, that it re- 

 quires no particular description. It is sold of three 

 different kiifds, viz. brown, white, and soft soaps. 

 It is the two latter kinds which ?.rc chiefly used in 

 bleaching ; the former being commonly sold for house- 

 hold washing in some parts of Britain. 



IV. Of all the agents used in bleaching, there is 

 none of them which ranks higher for giving facility 

 and dispatch to the various operations than the oxy- 

 muriatic acid. 



We might even at this moment have been unac- 

 quainted with the cause of the destruction of the co- 

 louring matter of vegetable substances, if the disco- 

 very of this acid, and its effects on colouring matter, 

 had nut pointed it out to us. For this discovery, 

 and its inestimable advantages, the arts are indebt- 

 ed to the celebrated Scheele. While employed in 

 making experiments on manganese, about the year 

 1774, he noticed it6 powers in rendering vegetable 

 substances colourless, mbre as a matter of curiosity 

 than of use. Having communicated his observa- 

 tions to Berthollet, in France, about the year 1786, 

 the latter lost no time in applying the properties of 

 this curious and interesting substance to the most im- 

 portant practical purposes. His application of it to 

 the bleaching of cotton ;*nd linen cloth proving suc- 

 cessful, he published the result of his experiments in 

 the year 1789. The new method of bleaching was 

 quickly and success! nlly introduced into the manu- 

 factories of Rouen, Valenciennes, and Courtray ; and 

 soon after into those of Manchester and Glasgow ; 

 and it has since been generally adopted in Great Bri- 

 tain, Ireland, France, and Germany. The advanta- 

 ges which result from this method of bleaching, in 

 every season ot the year, can be best appreciated by 

 commercial people who experience its beneficial ef- 

 fects in many ways, but particularly in the quick 

 circulation of their capitals. 



Great difficulties at first impeded its progress, ari- 

 sing chiefly from prejudice, as well as from the igno- 

 rance of the bleachers in chemical processes. These 

 obstacles were however soon removed by the assist- 

 ance of several eminent chemists at Glasgow and 

 Manchester, particularly Messrs Watt, Henry, and 

 Cooper. See p. 577, Note. 



Mr Berthollet's process for forming the oxymu- 

 riatic acid, consisted in distilling one part of the 

 black oxide of manganese with two parts of miiria T 

 lie acid, in a glass retort : the product of the distilla- 

 tion was received in glass bottles, properly applied, 

 when the quantity was small, or into a receiver lined 

 with lead when the quantity was larger. 



From the volatility of the oxygen as united with 

 c muriatic acid, when simply diffused in water, 



BLEACHING. 



with which it has a very slight affinity ; and, conse- Bleaching, 

 quently, its unequal action on the good6 which were *" 

 immersed in it for the purpose of being whitened, 

 and its discharging those colours which were wove 

 into the goods intended to remain permanent ; as 

 well as the suffocating vapours arising from it pro- 

 ving hurtful to the health of the workmen employed, 

 it soon became evident, that the application of it in 

 an extensive manner would be impracticable if these 

 difficulties were not more or less removed. Various 

 attempts were made to effect this ; and since it has 

 been accomplished, a number of persons have put in 

 their claims as the inventors of so advantageous an 

 improvement. Mr Higgins of Dublin and Mr B<-r- 

 thollet had both combined the ox>. -id with 



potash, so early as the year 1788. The km w'.edge 

 of the latter's having done bo, ai.d that the acid was 

 thereby deprived of its offensive smell, induced the 

 bleachers at Javelle, in France, to add a scii.tion of 

 caustic potash. Hence the oxymuriatic acid com- 

 bined with an alkali, is usually known by the name 

 of the Javelle liquor. 



Notwithstanding this evident improvement, it was 

 still generally maintained by chemists, that the oxy- 

 muriatic acid, united simply with water, possessed 

 greater bleaching power than that which is combined 

 with caustic alkidi ; but this was contradicted by the 

 practical bleachers, whose experence taught them, 

 that though the acid, thus combined with an alkali, 

 whitened with somewhat less rapidity, it had the ad- 

 vantage of retaining the gas much longer in open ves- 

 sels, and of preserving fixed dyed colours, such as the 

 Turkey or Adrianoplc-red. These facts are now so 

 fully established, that although several attempts have 

 been made, since the year 1796, again to introduce 

 the oxymunatic acid, diffused simply in water, into 

 air tight vessels, to prevent its offt nsive smell, yet, 

 from a conviction of its absurdity, it has been adopt- 

 ed only by a few. 



In order to produce the oxymuriatic acid, bleach- 

 ers follow different methods to obtain a liquor which 

 tlu-y suppose possesses the highest bleaching powers. 

 In one point they generally agree, which is, in gi- 

 ving a superabundance of the materials employed, by 

 which they are certain of procuring a liquor which 

 possesses high bleaching powers. Ore of the most 

 common proportions of materials employed for ma- 

 king this acid, is to take equal parts, by weight, of 

 common salt and manganese, which are intimately 

 mixed together. Some bleachers moisten the mix- 

 ture with water, to the consistence of a thick paste, 

 so that the dissolved salt may incorporate more inti- 

 mately with the manganese. An equal weight of 

 sulphuric acid is taken as of the other m- terials, 

 which is diluted with its bulk of water, and allowed 

 to cool before being poured inio the retort on the 

 combined salt and manganese. The charge for the 

 distillation thus consists of equal parts of salt, man- 

 ganese, and sulphuric acid, diluted with an equal 

 bulk of water. 



In the above proportions of the materials, it is evi- 

 dent, that the quantity of sulphuric acid employed is 

 more than sufficient for expelling the muriatic acid 

 from the salt ; two-thirds of the former acid being 

 enough to disengage the latter at a moderately high 



3 



