Correspondence

1872 Scientific American  
BEOll'ES ADD EXl'EBIlrtENTS, The follOwing recipes and experiments have not been practieally tested by the edilor of the SCmNTIFIC AMERICAN, but are published for the benefit of readers who may desire to 11"' them. Tile editor would be glad to be informed of the results of such trials. W ASlIING CoMPoUND.-The use of 80da for washing linen is very injurious te the ti�sue. and imparts to it a yellow color. In Germany and Belgium, the following mixture is now extensively and beneficially used: 2
more » ... eficially used: 2 Ibs. of soap are dis· solved in about is gallons water a� hot as the hand can bear it: then next is added to this fiuid , three large aized table· spoonfuls of liquid ammonia and one spoonful of best oil of turpentine. The!18 fiuids are incorporated rapidly by means of beating them together with a small birch broom. The linen is then soaked in this liquid for three hours, care being taken to cover the washing tub by a closely fitting wooden cover. By this means the linen is thoroughly cleaned, saving much rubbing, time and fuel. Ammonia does affect the linen or woolen goods, and is largely used as a washing liquor in the North of England. GOLD POWDER.-Gold powder for gilding may be prepared by putting iDto an earthen mortar some gold leaf, with: a lit· tle honey or thick gum water, and grinding the mixture till the gold is reduced to extremely minute particles. Wnen this is done, a little warm water will wash out the honey or gum,leaving the gold behind in a pulverulent state. An· other way is to dissolve pure gold, or the leaf, in nitro·mu riatic acid, and then to precipitate it by a piece of copper, or by a solution of sulphate of iron. The precipitate (if by copper) must be digested in distilled vinegar, and then washed (by pouring water over it repeatedly) and dried. This pre cipitate will be in the form of a very fine powder. It works better and is more easily burnished than gold leaf ground in honey as above. CEMENT FOR MARBLE AND ALABASTER.-According to Ransome, the following mixture affords an admirable cement for marble and alabaster: Stir up to a thick paste, by means of a solution of s hcate of soda (wat"r glass), 12 parts Portland cement, 6 parts prepared chalk, 6 parts fine sand, ,1 part of infusorial earth. Au irregular piece of coarse grained marble [OCTO�ER 26, 1872.
doi:10.1038/scientificamerican10261872-259b fatcat:qbc2agn6l5dpvptqnphzjwywuq