412 



CHEMISTRY. 



[BUOAK, rro. 



CM* of pnamiinu fruit*. The red currant affords it in 

 great abundance. It produce* an acid called poetic acid, 

 i combine* with base* to form rait*. 



v. ,- shall now pea* on to consider a very important 

 class of bodies, of which cane-sugar is the type, and j 

 from which a vast variety of article* of food and medicine 

 may be obtained. The following, a* well as the pro. 

 oediugly-named substance*, are, a* we ahall observe, 

 composed of oxygon, hydrogen, and carbon only. 



VB. This important article of food may be ob- 

 tained from VM.OIII source*. That used in this country 

 is tin- prelim- -f the sugarcane, so largely grown in 

 1 countries. The canes, when ripe, are cut down 

 and conveyed to rolling-mills, between the rollers of 

 which they are paased, so as to squeeze out the juice. 

 This, when obtained in quantity. U heated ; and slaked 

 lime is added to clarify it. The clear liquid is then 

 quickly evai>orated and crystallised, being repeatedly 

 stirred^ to prevent the formation of large crystals. It 

 is then drained to remove the molasses. Loaf-sugar is 

 made from the product of the above process, purified by 

 the addition of blood, A-c. , with which it is heated. The 

 albumen separates all foreign matter ; and thus sugar in 

 a pure form may bo obtained. In France, the beet-root 

 is largely cultivated for the purpose of producing sugar ; 

 and in North America, large quantities are obtained from 

 the maple-tree. The sap of this tree is obtained by 

 " tapping," the juice being afterwards purified in a 

 similar manner to that already described. Sugar, as we 

 ball presently see, is produced from many sources, both 

 of a vegetable and animal nature. Amongst the latter we 

 may mention the sugar of goat, asses, and human milk. 



Sugar, however, differs essentially in its chemical 

 characters, according to the source whence it is obtained. 

 Kr< >m fruits such as the gra|>e from honey and urine, 

 during the disease of diabetes, the kind called grape- 

 sugar is producible. This sort has not the sweetness 

 of cane-sugar. It differs also in the form of its crystals, 

 and in its less solubility in water. 



The following table exhibits the chemical composition 

 of various kinds of su^ar : 



Cane-sugar C,., II, , O,, 



Grape ..C,, H lt O. 



HOi 



C,,, H.~ O, 



Cane-sugar may be converted into grape-sugar by 

 means of dilute sulphuric acid. 



A peculiar sugar, termed manm'te, may be obtained 

 from some plants, as the ash ; it is the ordinary manna 

 of commerce, and is composed of C 12 H, 4 (>,._,. 



Owing to the great demand for milk sugar in the 

 homoeopathic system of medicine, an immense quantity 

 of this substance is now produced. Of this, some finely 

 crystallised specimens were exhibited in the International 

 Exhibition of 1802 ; they were produced in Switzerland, 

 from the milk of goats. 



We shall now proceed to speak of the various sub- 

 stance* which may be obtained from sugar, by chemical 

 and manufacturing processes. 



OXALIC ACID. If sugar be heated with dilute nitric 

 acid, the well-known oxalic acid is produced. The nitric 

 acid part* with its oxygen, and so oxidises the sugar : 

 crystals of the oxalic acid may thus be obtained, having 

 a composition of C, O. + 3 HO, or a combination of 

 one equivalent of acid with three of water. In this 

 curious metamorphosis wo have an astonishing change 

 occurring between the material employed and the re- 

 sulting product The former, an article of food in 

 universal request amongst all nations, may readily be 

 converted into a most virulent poison, by comparatively 

 simple means, affording another instance of the sur- 

 pnxing changes which chemistry continually affords us. 



Oxalic acid, if heated with sulphuric acid, uu.l.-i-- 

 goes decomposition, carbonic acid and carl" 

 being produced. With IUINCA, it forms the salts called 

 oxalate*, of which the biuoxalate of potass and the 

 oxalate of ammonia are the most important The salt 

 of potass exist* in the plant called sorrel, and also in the 

 English kind of rhubarb used as food, being the cause of 



its sour taste. It is sold in the shops as salts of sorrel, 

 and U used for taking put ink-marks from linen. 

 having the power of forming a soluble salt with protox ido 

 of iron. Oxalate of ammonia is chiefly used as a chemi- 

 cal test for liinu, with which it forms an oxalate of lime, 

 as an insoluble white powder. Oxalic acid unites also 

 with oxides of metals, such as those of iron, copper, 

 nickel, <tc. 



Saccharic acid may also be produced by the action of 

 dilute nitric acid on sugar, it is composed of (.',._, Il g 

 (), ( -f- 2 HO. Mucic acid is obtained by the action of 

 nitric acid on gum, and the sugar of milk. Its compo- 

 sition is Cj, H g O u + 2 HO, and is therefore analogous 

 to saccharic acid. 



AM .iiini.. This well-known liquid is the product of 

 the vinous fermentation of grape-sugar. It is sold in 

 commerce as spirits of wine. And to its presence in 

 brandy, gin, rum, whiskey, wines and beer, their peculiar 

 effects of producing intoxication are due. Alcohol is 

 readily produced by adding yeast to a solution of * 

 in water, at a temperature varying between 70 and 80 

 Fahrenheit. Carbonic acid is largely disengaged ; and 

 when fermentation is complete, and the liquid has be- 

 come clear, it must be distilled in a retort, the first por- 

 tions only being retained. The product is alcohol largely 

 diluted with water. By repeated distillation with suli- 

 carbonate of potass, or dry lime, the water may 1 o 

 separated, until nearly absolute or pure alcohol is 

 obtained. In its pure state, alcohol has a composition 

 of C t H 8 O 2 ; compared with water = 1000, its specific 

 gravity is 0794. It boils at 173 Fahrenheit ; and is 

 converted into a vapour which is readily condensed, 

 and which, like the liquid itself, is highly inflammalile. 

 " Proof spirit," such as is referred to in the excise laws, 

 contains half pure alcohol, the remainder being water. 

 Its specific gravity is 0-92 nearly. The uses of alcohol 

 are very numerous in arts and manufactures. From its 

 solvent powers it is used to make varnishes ; but for 

 this purpose, methylated spirits are now employed, of 

 which we shall have to speak hereafter. 



The most important use of alcohol U that of a beverage ; 

 and to this point we shall now direct the attention of 

 our readers. 



From our preceding remarks, it will be gathered that 

 the fermentation of saccharine matter leads to the pro- 

 duction of alcohol in all cases. This is strictly true ; but 

 the commercial products differ according to the source of 

 the sugar. Thus, whiskey is obtained by the fermenta- 

 tion of the sugar of malt, as in beer. Kuiu is pro- 

 duced when coarse cane-sugar is employed. lirandy 

 and wines, generally, are the produce of the juice of the 

 grape. The differences of these liquids, then, are owing 

 to the admixture of the alcohol they contain, with other 

 substances dissolved and held in solution by it. In corn 

 spirit, or that obtained from potatoes, a coar.>e offensive 

 oil is found, which gives the peculiar smoky flavour of 

 whiskey. In wines, the peculiar and distinguishing 

 taste is due to the presence of an ether, which, at the 

 same time, differs in each wine, and gives it its character- 

 istic flavour and so on. Again, the per-centage of pure 

 alcohol varies greatly. In London porter, it does not 

 exceed 3 or 4 per cent. ; whilst in Spanish wines, such as 

 sherry and port, as much as 20 to 30 per cent, is found ; 

 and brandy often contains as much as 60 per cent, of 

 pure spirit. Although, therefore, the same chemical 

 principles are involved in the manufacture of each kind 

 of spirituous or fermented beverage, the modes of 

 manufacture differ greatly. Beer, the favourite beve- 

 rage of our own country, is produced from malt. Malt 

 is produced from barley by a process which produces 

 germination, and the simultaneous conversion of the 

 starch of the seed into sugar. This is effected \,\ moist- 

 li- toi il, \vhich should be kept together in masses; 

 it thus heats, but is prevented from gaining too high a 

 temperature by Ix-ing repeatedly stirred on the malting- j 

 floor. It is then kiln-dried, which utops any further 

 change. During iln. process a substance called (Hastate 

 is produced, which, acting on the starch, converts it, 

 eventually, into sugar. 



