MECHANICS AND USEFUL ARTi. 99 



clean tallow or white wax should he previously added to the starch when it 

 is bcin^ mixed with the water. When starch is to be used for coarse fabrics 



O 



for the purpose of rendering them fire proof, muriate of ammonia may be 

 employed with the phosphate of ammonia, and in that case the phosphate of 

 ammonia is to be diminished in proportion to the quantity of muriate of 

 ammonia added. 



RENDERING STUFFS WATER-FROOF. 



The following is a description of a method patented by M. Menoti, of 

 France, for rendering stuffs water-proof, and yet allowing them to remain 

 permeable to air. We translate the French measures, assuming the litre 

 as a quart, and the kilogramme as two and a quarter pounds avoirdupois. 



Take two vessels of a capacity of five gallons each ; place in one twenty- 

 tAvo pounds of alum ; in the other, nine pounds oleic acid, and one and a 

 half gallons alcohol. Stir this mixture well, and pour it into the first vessel, 

 taking care to stir well with a wooden ladle during the mixture, and for ten 

 minutes afterwards. Let the mixture stand for twenty-four hours, then de- 

 cant the oleic acid and alcohol which are floating on top. Throw the pre- 

 cipitate upon a felt filter, and press until all the liquid is run out. Take the 

 precipitate from the filter and dry at eighty-six degrees ; when dried, powder 

 it by rolling it upon a table with a wooden roller. This compound the 

 author calls liydrofugine. To use this, dissolve it in 1 50 times its weight of 

 warm water for woollen stuffs, while for linen, cotton, or silk, 100 times the 

 weight will be enough. Filter the solution through linen, and plunge the 

 stuffs to be water-proofed into it ; soak them well, then take them out and 

 wring them ; soak them a second time, then take them out and dry them 

 either in the air or before a fire. The stuffs, when Avell dried, are impermea- 

 ble to water, but not to air. The quantity of liydrofugine necessary cannot 

 be accurately determined, but generally one ounce is enough for two yards 

 of cloth or four of muslin. 



M. Thieux, of Marseilles, proposes a simpler process. In two vessels, 

 each of a content of twelve gallons of river water, are dissolved, in the one 

 three and a half pounds of alum, in the other the same weight of sugar of 

 lead. When the solutions are complete, pour the liquids together, by which 

 will be formed an insoluble sulphate of lead, and soluble acetates of alumi.n 

 and potassa, mixed with a slight excess of alum. As soon as the liquid lias 

 become clear, it is drawn off and the stuffs plunged into it ; they must be 

 strongly compressed while under the liquid, to expel the air from their pores, 

 and then suffered to soak for at least four hours, so as to insure the perfect 

 penetration of the liquid everywhere. When withdrawn they are lightly 

 shaken, then dried, brushed, and pressed with a hot iron. It appears that 

 various specimens of cloth experimented on by a committee, absorbed 

 from eleven to seventeen per cent, of their weight of saline matters, and re- 

 tained their original appearance, and their pliability at all temperatures. 

 But after immersion in fresh water for twenty-four hours, they lost all their 

 additional weight. As to the efficacy in this process, there appears to be 

 a very serious difference of opinion ; the conclusions of a committee ap- 



