188 [ 175 3 



5. That water, alcohol, the acids, and even the alkalies, do not en- 

 tirely dissolve, equally well as the soap^ the matters contained in the 

 silk; and that this agent ought to continue^ to be exclusively preferred 

 in the cleansing of silks, to all the above substances. 



6. That the oxi-muriatic acid changes the properties of the gum, di- 

 minishes its affinity to water, and assimilates it to the resins, by ren- 

 dering it soluble in alcohol. 



7. That the silk, after being separated, by cleansing, from all the 

 substances which concealed its whiteness and its brilliancy, loses af- 

 terwards in this bath, by the continued action of the soap, all the pro- 

 perties that it acquired by it; becoming dull, stiff, and colored, by the 

 solution of more or less of its texture; a solution which is effected by 

 all liquids, and which takes place even in boiling water. It is to this 

 cause, hitherto unknown, that we must attribute the impossibility of 

 impregnating the silks, whilst hot, with alum, and the destruction of 

 a part of their brilliancy, in all the colors somewhat brown, for which 

 we are obliged to employ the heat of boiling water. 



8. That these great inconveniences may be obviated, by causing the 

 silks to be boiled no longer than is necessary for cleansing them com- 

 pletely; and by submitting them only to moderate heats, in all the 

 operations of dying. 



9. That copper vessels cause some trouble, owing to the ease with 

 which they oxidate, and discolor the silk, as has been shown in his 

 memoir on aluming. 



10. That it is highly important to employ very pure water, free 

 from calcareous impregnation, but not in unnecessary quantities, in 

 order not to increase the proportion of injurious salts, and not to weak- 

 en the force of the solvent. 



The proper proportions for this operation,, as ascertained after many 

 experiments on a large scale, are seven or eight pounds of water to one 

 of silk; and one-twelfth, or one-sixth, is sufficient for the greater num- 

 ber of colors: for yellow unbleached silks, and, above all, for those 

 of Grenada (Spain) it is necessary to add from 50 to 60 per cent. The 

 greatest quantities do not produce a very sensible effect upon those silks: 

 for we cannot make them as white as those unbleached white silks 

 cleansed with 25 per cent, of soap, even by the combined action of equal 

 weights of soap and sulphureous gas. 



11. Experiments have shown that all silks are completely cleansetl 

 in less than an hour; and that they lose their coloring and waxy mat- 

 ters, in proportion to the quantity of soap v/hich the cleansing bath 

 contained. 



12. The operations of ungumming, boiling, and bleaching, which 

 take up six hours, may be reduced to one operation, of an hour, with 

 tlie same quantity of soap. I propose, then, the following method to 

 cleanse silks. To boil, for an hour, all yellow and white silks, with 

 five parts of water to one of silk, and a quantity of soap, which may 

 be determined according to the colors intended to give them ; to put 

 the silks and soap in the water only half an hour before the moment of 

 ebullition, taking care to turn them often, Ivong boiling causes the 



