On the Art of Dying by colourid Oxydes of Tin. 1 79 



« inftead of the acetic. But this folution, which becomes more and more oxygenated as it 

 « dries, and fucceflively difengages a portion of acid, weakens the cotton or the linen, which are 

 " impregnated With it ; but wool and filk fuffer lefs. To avoid this inconvenience, it is ne- 

 " ceffary to defend the piece by a folution of one part of Marfeilles foap, and fixteen of 

 " water *. The article, after drying, is to be plunged in the muriatic folution of tin diluted 

 " with water, and when well waihed, it may be dyed. The colours obtained by means of 

 " foap are more lively-|-." 



The author here makes a very important remark with regard to the play of the affinities ;• 

 namely, that in order to have the coloured oxydes of tin beautiful and folid, it is neceflary that 

 there fhould remain a fmall quantity of combined acid ; and that neverthelefs the fame. colours 

 are obtained upon goods dyed by the intermedium of the folutions of tin, though thefe goods 

 may have been previoufly pafled through boiling water, which muft neceffarily carry off the 

 fait or acid which might remain, and prove an impediment to the attradlion of the colourino- 

 parts. The author inclines to attribute this effeft in linens and cottons to part of the gum, 

 with which they are impregnated, remaining combined with the oxyde, and ferving inftead of the 

 acid, while in wool and filk the animal part a£ls in a firnilar manner. 



Faffing afterwards to the operations made with the alkaline folutions of the coloured oxydes, 

 which he fuccecded in obtaining, deprived of all caufticity, he gives the following defcription. 

 " I commonly ufe for thefe folutions, when the coloured oxyde is in the form of powder, a fo- 

 lution of potafh made with one part of the carbonate of potaih in cryftals, one part of lime, and 

 eight parts of water. After decantation, and reducing the liquid to one-half, I pound and ftir 

 well the powder with this liquor. The reduction of the fluid is to be made to one-fourth, when 

 the oxyde is intetided to be difldved fimply as it comes from the filter without drying. It is thus- 

 put into a veflel, and fhaken with the fluid. 



" To avoid an excefs of potalli, the folution mufl: be poured a little at a time upon the 

 oxyde, and fome oxyde muft be kept in referve, in cafe too much alkali fhould have been added. 

 This may be eafily known by applying a fmall drop to the tongue. 



" When thefe folutions do not poffefs fufficient confiftence, they muft be gummed. By this 

 means they become applicable by the block or the pencil. They fix upon the cotton or linen 

 the coloured oxydes, which, by fome weeks repofe, attradl the carbonic acid of the atmolphere, is 

 with which the alkali becomes (aturated bv decrees. 



" 1 he precipitation of thefe oxydes may 1-ikewife be made fpeedily, and immediately after the 

 piece is dried, in which method the colours are alfo more vivid. For this purpofe nothing more is 

 requifite but to fteep the piece for fifteen minutes in a Muriatic folution of tin, diluted with twenty 

 parts of water, or, which is better, in a folution of fulphate of alamine made with eight parts of 



* I have given in the Annates de Chemie preparations of foap, which may be ufed inftead of that of Mar- 

 feilles. Note of rhe author. 



t Journale de Phyfique Pluvoife. Annual Regifter, vol. v. p. 114, where the entire menaoir is. to be 

 foutiid. 



