CHEMICAL SCIENCE. 271 



" The letter should be lightly once brushed over with diluted muriatic acid. 

 As soon as the paper is thoroughly damped, it must be again brushed over 

 with a saturated solution of yellow prussiate of potash, when the writing im- 

 mediately reappears in blue. In this latter operation, plenty of the liquid 

 should be employed, and care must be taken that the brush is not used so 

 roughly as to tear the surface of the paper. This result is obtained by sim- 

 ple chemical laws, as the iron which exists in the writing-ink is retained in 

 the fibre of the paper, and by the action of the ferrocyanide of potash, 

 Prussian blue is formed the acid being used simply to place the iron under 

 favorable conditions for uniting with the ferrocyanide. The letter should 

 then be washed in a basin of clean water, and dried first between the folds 

 of blotting-paper, and subsequently by holding it before the fire, when the 

 letter is fit for the counting-house. If the letter should be of much perma- 

 nent value, I recommend it to be carefully sized with a solution of isinglass 

 before being filed; but if the paper has been much rotted, the operation 

 requires care, and should not be done until a notarial copy, or photograph, 

 has been taken." 



WAX AND ROSIN FOR PAINTING. 



To oil-coats there is this objection, that they require a comparatively long 

 time to dry. When oil of turpentine is used, though it evaporates fast 

 enough, it leaves the painting soft; and although, by the addition of some 

 other substances the drying may be hastened, it even then takes up too 

 much time, and leads to the substitution of white-wash and other water- 

 colors. Mr. Alluys now proposes a mixture which yields a coat of paint 

 that will dry as fast as white-wash, but leave as durable and elastic a coat 

 as that of oil. To prepare it, instead of more linseed oil, as usually, he adds 

 to the paint, ground in oil, a solution of wax and rosin in spirits of turpen- 

 tine. The mixture thus prepared has the appearance of common oil-paint, 

 and acts like such : on the evaporation of the turpentine, it leaves a coat 

 sufficiently hard to bear gentle rubbing without coming off. Barreswil has 

 reported some experiments with this mixture, and finds that, although it 

 becomes sufficiently dry and hard after a time, it does not equal a good oil- 

 coating in this respect; but he has no doubt that for some purposes Alluy's 

 mixture will be found quite desirable. He gives the following formula for 

 its preparation : Ten parts of pure yellow wax are dissolved in the same 

 quantity of linseed oil, and five parts of rosin in eight of spirits of turpen- 

 tine, at a slow heat, in separate vessels, until quite liquid, when they are 

 taken from the fire and mixed, with constant stirring until they thicken. 

 In this condition the mixture serves for out-door and store-work. If to be 

 applied with ground paints, it is thinned with spirits of turpentine as 

 required. Dingier' s Journal. 



ON THE COMPOSITION AND PREPARATION OF ARTIFICIAL FRUIT 



ESSENCES. 



Amyl Alcohol, Fusd Oil, CioHi202. This alcohol, which has been referred 

 to as an impurity of alcohol, is contained in the products of fermentation 

 of potatoes, grain, and grape husks. To obtain it in a state of purity from 

 the ordinary grain fusel oil, which may be obtained at distilleries, the crude 

 fusel oil is agitated with an equal bulk of water, the water removed, and the 

 oil distilled with about its own weight of dry carbonate of potassa. The 



