CHEMISTRY APPLIED TO THE ARTS. 



the ethics of this question, which do not seem 

 to present any great difficulty, but describe the 

 methods used for obtaining good wine from grapes 

 containing too little sugar and too much acid, and 

 for increasing the quantity of wine obtainable from 

 a given quantity of grapes. One method of im- 

 proving the ' must,' or juice, is to evaporate away 

 part of the water, either after pressing the grapes, 

 or by allowing the grapes to dry partially before 

 they are pressed. By this method the acid is 

 concentrated as well as the sugar, and the yield is 

 diminished. 



The second method, that of Chaptal, consists in 

 adding glucose, prepared from starch, so as to 

 make up the quantity of sugar to 20 per cent. 

 By this method the wine is strengthened, but the 

 excess of acid remains. This may be cured by 

 adding normal tartrate of potash, which forms 

 with the tartaric acid bitartrate of potash, which 

 is mostly precipitated. 



A third method is now practised to a consider- 

 able extent. It is called Gallising (Ger. Gallisiren), 

 from its inventor, Dr L. Gall. It consists in dilut- 

 ing the juice with water till it contains the right 

 proportion of acid (about 6 parts in 1000), and 

 then adding glucose to make it up to 20 per cent. 

 By this means a juice is obtained, which, as far 

 as the water, acid, and sugar are concerned, 

 resembles the natural juice of a good grape. At 

 first, it was feared that the bouquet of the wine 

 would suffer by the dilution, but it has been found 

 that the grape contains far more than enough of 

 the materials from which the bouquet is formed to 

 perfume all the wine that can be thus made. This 

 discovery was made by M. Pe*tiot, who utilised it 

 by introducing a method for greatly increasing the 

 yield of wine. This method (Pe"tiotising) consists 

 in pouring upon the 'marc,' or solid matter re- 

 maining after the juice has been expressed, a 

 quantity of water containing 20 per cent of glucose, 

 .and allowing this to ferment : the resulting wine 

 has the bouquet characteristic of the original wine. 



Champagne and other sparkling wines are pre- 

 pared by adding to young wine in the bottle 

 a certain quantity of glucose, then corking them 

 up, and allowing the added glucose to ferment ; 

 the carbonic acid produced dissolves in the wine. 

 Cider and Perry are prepared from apples and 

 pears in much the same way as wine is prepared 

 from grapes. 



Beer, ale, and porter consist of the fermented 

 infusion of malt, flavoured with hops. The various 

 kinds of malt liquor differ from one another in 

 the amount of alcohol, of sugar, of extractive 

 matter from the malt, and of bitter substance from 

 the hop. The dark colour of porter is produced 

 by the addition of malt dried at a high tempera- 

 ture, so that part of the sugar is converted into 

 caramel. 



DISTILLED SPIRITS whisky, brandy, rum, gin, 

 .arrack, &c. consist of alcohol and water, along 

 with peculiar flavouring substances, either derived 

 :from the material used, or purposely added. 

 Thus, the flavour of whisky is mainly due to the 

 presence of small quantities of amylic alcohol ; 

 that of brandy, to cenanthic and other ethers 

 rfrom the wine ; that of rum, to butyric ether. Gin 

 ds flavoured by adding oil of juniper-berries to a 

 mixture of alcohol and water. The brown colour 

 of brandy and rum is given to them by the addition 

 of burnt sugar (caramel). The yellowish colour 



of whisky is caused by tannin absorbed from the 

 casks in which it is kept. 



The alcoholic fermentation is made use of in 

 the manufacture of bread. Wheat-flour consists 

 chiefly of starch and an albuminoid substance 

 called gluten, which forms a stiff paste with water. 

 When yeast is added to the dough, part of the 

 starch is converted into glucose, and this ferment- 

 ing gives alcohol, which escapes by the chimney 

 of the oven, and carbonic acid, which forms 

 bubbles in the dough, thus giving the bread its 

 spongy character. 



GUNPOWDER. 



The invention of gunpowder was formerly 

 ascribed to the Benedictine monk, Berthold 

 Schwarz, of Freiburg, in Breisgau, who lived 

 about the year 1334; but it is now certain that 

 it was known much earlier, at least as far back 

 as the eighth century. 



The action of gunpowder depends upon the 

 fact that, when kindled, it burns rapidly, giving 

 out a great quantity of gas. If the combustion 

 takes place in a closed vessel, an enormous pres- 

 sure is produced, partly owing to the quantity of 

 gas produced, partly owing to the high tempera- 

 ture to which it is raised. Many substances are 

 known which have the same property, but some 

 of them are unsuitable for the purposes of gun- 

 powder, because they are too easily exploded, and 

 are therefore dangerous ; or are too expensive ; or 

 explode too suddenly, so as to shatter the gun- 

 barrel ; or give rise to products of combustion 

 which act destructively on metal. 



Thus, although there are, as we shall see, sub- 

 stances which for certain purposes may be used 

 instead of gunpowder, and are even more con- 

 venient, still gunpowder retains its place for its 

 own special use as ^//powder. 



Gunpowder is an intimate mixture of charcoal, 

 sulphur, and saltpetre. The charcoal is prepared 

 by heating soft wood (alder or dogwood) in a 

 cylindrical retort (see CHEMISTRY). The sulphur 

 is distilled sulphur. The nitre is recrystallised in 

 small crystals, so as to allow the mother-liquor 

 which contains the impurities (chiefly chlorides) 

 to drain away. 



The ingredients having been reduced to powder, 

 and sifted, are roughly mixed in a revolving drum 

 of gun-metal, and then in quantities of about 50 

 Ibs. at a time, more thoroughly mixed in the 

 ' incorporating mill.' Here the mixture is sprinkled 

 with a little water, and rubbed and ground by 

 means of two cast-iron rollers, working upon a 

 cast-iron bed. After from three to five hours' 

 grinding, the ' mill-cake,' as the mixture is now 

 called, is removed, and exposed for a quarter of 

 an hour between copper plates to a pressure of 

 70 tons per square foot The ' press-cake ' thus 

 formed is then broken up into grains. The object 

 of this granulation or 'corning' is to allow the 

 powder to ignite rapidly by leaving spaces between 

 the granules for the passage of flame. The powder 

 is then passed through sieves of different sizes of 

 mesh, so as to sort it into the various degrees of 

 fineness. The grains are next polished or ' faced ' 

 by being shaken together in a revolving drum. 

 The larger-grained powder is sometimes 'faced' 

 with graphite (black-lead), a little of that substance 

 being put into the drum along with the powder. 



