ISOj.] 



Chemical Experiments in Dying Cotton. 



It is proper here, to remark, that, in 

 place of foda, pot-afh, which is fold at a 

 much clieaper rate, may be employed to 

 ■anfwer the lame piirpoCe. 



It follows, from thefe principles, that 

 unlefs the foda and oil pofi'efs certain qua- 

 lities, they cannot be employed with ad- 

 vantage. 



It is necelTary that the foda be cauftic, 

 and contain little or no muriate. 



Lime cannot be employed to rendet it 

 caullic, as it fpoils its colour. Its caufti- 

 city mul be the effecV of calcination. 



The carbonate of foda, and that which 

 contains rnuch muriate, combine very im- 

 pel feiftly with oil ; confequently neither 

 foda in an efrlorefcent ftate, nor the im- 

 pure foda of commerce, can be employed 

 lor tMs dye. 



The clioice of tlie oil is equally eflTen- 

 tial as that of the foda. 



If the oil be of a gond quality, it will 

 pel leflly Incorporate with the alkaline lixi- 

 vium, and remain in a ftate of permanent 

 combination with it. 



The moiV proper oil for tins purpofe is 

 not that which is puie, but, on the con- 

 trary, contains a confiderable portion of 

 the extradlive principle. 



The firft docS not remain in a flate of 

 combination with the alkaline lixivium. 

 It requires even that the ley fhould be 

 ftrongei.j a circuniftance which does not 

 allow the. dyer to regulate the fubfeqnent 

 operations. 



The fecond enters into a more intimate 

 and durable union, and requires only a 

 weak ley of one or two degrees of 

 ftrength. 



The receffity of an intimate and per- 

 manent incorporation of the oil and alkali 

 muft be evident, if we reflefl, that the ley 

 is merely ufed to divide, dilute, and con- 

 vey the oleaginous fluid uniformly into 

 all the parts of the cotton 5 for if the oil 

 be not well incorporated, the cotton pafied 

 through the mordant will felze on the oil 

 unequally, and hence the colour muft be 

 bad. 



The whole art in producing an uni- 

 form and confident colour confiits in the 

 choice of go(;d oil, and in a proper propor- 

 tion of foda. 



It follows, moreover, from thefe prin- 

 ciples, that the oil ought to be In excels, 

 and not in a ftate of perfect faturation ; 

 for otherwile it would abandon the fluff, 

 and the ctlnur be rendered fl it. 



When tht cotton is properly impreg- 

 nated veith oil, it is fubjefted to the ope- 

 ration of gslling. Hence the ufe of nnt- 

 galli has many advantages. Firft, The 



Monthly .Mag. No. 131. 



acid which they contain decompofes the 

 faponaccous liquor with whicli the cotton 

 is impregnated, and fixes the oil upon the 

 fluff. Secondly, The peculiar character 

 that galls polTels, predifpofes the cotton to 

 imbibe the colouring principle. Thirdly, 

 The aftringent principle combines witfi 

 the oil, and forms a compound whiih 

 blackens on drying, is little foluble in wa- 

 ter, and has the greateft affinity with the 

 colouring principle of madder. 



An example of this laft combination is 

 furniflied by mixing a deco£lion of nut- 

 galls with a folution of foap. 



Hence it is evident, from thefe princi- 

 ples, I. That other allringents cannot 

 fnpply the place of galls, in vjhatever 

 proportion they may be employed.— '2. 

 That the galls fliouid be ufcd as warm as 

 pofiible, in order that the deccmpofition 

 may be rapid and complete. — 3. That the 

 galled cotton Pnould be dried expediti- 

 oufly, to prevent its acquiring a blackirti 

 hue, which would injure the brilliancy of 

 the red colour we willi to impart to it.— 

 4. That we ought to choofc dry weather 

 for the operation of galling, becaufe a hu- 

 mid air proving unfavourable for dying, 

 obfcures the beauty of the colour. — 5. 

 That the cotton ought to be prefTed with 

 the greateft care, in order that thedecom- 

 pofition may be effefted uniformly over 

 every point of its furface.— 6. That it is 

 necelfary to eftablifli the juft proportions 

 between the nut-galls and Ibap ; for if the 

 firft predominates, the colour will be 

 black ; if the fecond be inexcefs, the poi'- 

 tion of oil which is uncombined with the 

 aftringent principle will be difPipated on 

 vvafiiing, and the colour remain faint. 



The third mordant employed in dying 

 cotton red, is the fulphate of aUimine. It 

 not only pofTclTes the property of height- 

 ening the red tint of the madder, but alfo 

 contributes, by itsdecompofition, and the 

 fixation of its alumine, to impart durabi- 

 lity to the colour. 



In order to form a judgment of the ef- 

 feils of alum in the dying of cotton, it ia 

 only neceflary to mix a decoftion of nut- 

 galls with a folution of alum. The mix- 

 ture immediately becomes turbid, and 

 there is formed a gieyifli precipitate, 

 which, upon being dried, is inloiuble iti 

 water and in alkalies. 



What occurs in this experiment is 

 equally obfervable upon the addition of 

 alum to the dye. As foon as the galled 

 cotton is immerfed in a lolutlon ot ful- 

 phate or aciiite of alumine, its colour im- 

 mediately ch iiiges, and beconies greyilii. 

 The bath, indeed, prelims not any ap- 

 D pcarai;ce 



