On Bleaching. 33 



parison hitherto used, and conckxde with giving some rules 

 for the adaptation of the valuable tables of Mr. Gilpin to 

 the present standard, together with two short tables of our 

 own, by which the comparative strength and value of any 

 spirit may be found, when its specific gravity and tempera- 

 ture are given. 



[To be continued.] 



V. On the Quantity of Iran in Cotton and Linen Cloth: Evil 

 EjfectSy simple Means of eradicating, &c. : and Obser- 

 vations on Bleaching, the Result of long Experience. By 

 ^/ICHOLAS Grimshaw, Esq. Member of the Diihlin 

 Society*. 



-C^VERY one who has attended to the process of bleaching, 

 must have observed a buff hue in the cloth after it had been 

 s.pread on the field, or immersed in oxygenated muriatic 

 acid (bleaching liquor) . 



Having thought much on the subject, tried experi- 

 ments innumerable, and being of opinion that ironf was 

 the cause, I, on the 22d of September last, cut a yard of 

 calico off one of the pieces then in the first bleaching- 

 liquor, which had been previously boiled in potash, which 

 piece (as well as many of the 100 then in the same kieve) 

 was a deep buff. The yard of calico was put into a hot so- 

 lution of sumach (astrmgent), and it soon became a deep 



* From the I'lainactions of the DtiWn Society, vol. i. part 2.— That iroa 

 is very gc-nerally ditfubtd throughout the globe, being frequently found 

 mixed with sand, clay, chalk, and in ihe ashes of vegetables, and even ia 

 the blood of animals, in such abundance, that fome authors have attri- 

 buted both the colours of vegetables, and of the vital fluid itfelf, to the 

 iron contained in them, is no new discovery: but, that the bad colour of 

 linen and cotton cloth is owing to the evil effects of the iron contained in 

 the vegetables, was hrst thought of by the author of the following cs- 

 s.iy, which is a strong proof of the great xitility of chemical knowledge 

 in brinjiing manufactvirts to perfection. 



t Since my arrival in Dublm, iVIr. Higgins, professor of chemistry, &c. 

 accompanied me to a nciglibonnng bleach- green : we cut a bit of cjlico 

 off a piece then in the first bleaching liquor, and which had had one boil 

 ill potavh: it was buH', and on trying it with marine acid and pruisiate of 

 potash it became blue: a convincing proof that iron was present. The 

 following experiments aiko were made in the presence of Mr. Higgins, 

 and his very respectable operating pupils, in the elaboratoiy of the 

 Dublin Society. Six ounces of unbleached calico was burned to tinder 

 in a crucible ; digested it with nirtriiie acid, and filtered it; poured prus- 

 riate of potash onihe solution, and found a copious precipitation of prus- 

 •iateofiron; filtered the liquor, having previotisly weighed the hirer- 

 (45 grains), and found when dry it had retained eight grains of the 

 pruskiate of iron. 



Six ounces of linen, treated in the same manner, produced six grains 

 of pri'ssiaterif iron. 



Vol. XVI.No. fii. C <lxab 



