Jdvantagts of Oxymurlate of Potajh in Dying. 159 



Having remarked the good eft'cdl which the oxygenated muriate of carbonated potafli 

 produced upon ink, I next tried if it would improve the colour of the fubftances commonly 

 ufed in dying. The aqueous extradt of galls by a fmall addition of this faline folution at firfl 

 becomes a little whit? and turbid, a little more immediately renders it as dark coloured as it 

 becomes by long expoCure to the adlion of the air and light; (till more of the inline folution 

 difcharges the dark colour, and changes it to a kind of yellow : but galls require a much 

 greater quantity of the fait to difcharge their colour, than any vegetable colouring fubftance 

 I have tried. The colours of logwood and weld, are rendered much brighter and more 

 intcnfe by the faline folution : cochineal and archil, are improved : the colours of brazil 

 wood and madder, are little altered. But if a folution of alum be poured into the aqueous 

 cxtradl from any of the abovementioned fubftances, and fufFered to remain at reft until no 

 more precipitate falls down, and if the clear liquor be then poured ofF, and a little of the faline 

 folution mixed with it, a very abundant and better coloured prscipitatc immediately fubfidcs. 

 By adding, alternately, folutions of alum and oxygenated muriate of carbonated potafli, 

 the whole of the colouring particles may be precipitated from the liquor, and thus a much 

 more abundant and better coloured precipitate procured, than could have been got by ufing 

 alum alone. Great caTe muft be taken not to add too much of the faline folution at one time, 

 for if any of the colour is difcharged, it cannot be recovered. It is likewife proper, to add 

 little of the alum at one time, for too much of it injures the colour, and the firft precipitates 

 are generally the beft. No heat muft be applied after the addition of the faline folution : the 

 colour of all the preparations I could make of indigo, was injured or difcharged by being 

 treated with this faline folution. 



As yet, I have tried the effect the folution of this fait would have upon the dying of 

 cotton with weld only, and in every inftance it has been an improvement where the fmall 

 pieces of cotton were of the fame quality, immerfed in the fame mordants and colouring baths, 

 for the fame length of time, with this difference only, that before one of them was taken out, 

 a little of the faline folution was added to the colouring bath, the colour was brightened by the 

 addition, and about one-third part lefs weld, produced the fame fhade as when none of the 

 faline folution was ufed. The bath muft be cold before the faline folution is added, otherwife 

 the colour will be injured; and I imagine that this fait will be employed to moft advantage, 

 where the ftufF to be dyed is immerfed in a cold colouring bath. It certainly has a tendency 

 to extraft the colouring particles from the dye, and to brighten them when cold, but in every 

 cafe injures, and, in fome cafes, entirely difcharges their colour when warm. 



I cannot precifcly fay, to what degree the carbonated potafli ought to be faturated with the 

 oxygenated muriatic acid, fo as to produce the beft pofiible effecl upon colours ; but I have 

 found, that the degree of faturation has a powerful influence, and, in many cafes, changes the 

 fliade of colour completely. Different colours alfo require different degrees of faturation in 

 the fait, fo that a great many experiments muft be tried before it can be exactly afcertained 

 what will anfwer beft in every cafe: for ink, it fliould be faturated to fuch a degree, as that 



Y 2 bubbles 



