CHAMBERS'S INFORMATION FOR THE PEOPLE. 



.-adulterations to add to the weight of the article. 

 We shall here describe the chief varieties of soap 

 which occur in the market, and the ways in which 

 they are prepared. 



HARD SOAPS. These are prepared by boiling 

 non-drying oils or solid fats with caustic soda 

 solution. The oil or fat is first boiled with a 

 -quantity of alkaline solution insufficient for its 

 complete saponification ; when all the alkali has 

 disappeared, salt is added, and the soap and ex- 

 cess of oil or fat rises to the surface, floating on 

 <he ' spent lye,' as the solution containing salt and 

 .-glycerine is called ; which, if the boiling has been 

 properly conducted, contains no alkali. When 

 ^complete separation has taken place, the spent lye 

 is run off. More caustic soda solution is then 

 -added, and the boiling continued until the mixture 

 lias a permanent and strong alkaline taste and 

 reaction. Salt is then added, which causes the 

 separation of the soap from the alkaline solution. 

 The soap is ladled out into what are called 'frames,' 

 in which it cools and solidifies. The ' frame ' is a 

 box, the bottom of which is pierced with holes, 

 and the sides of which are held together by means 

 of bolts, so that they can easily be taken asunder. 

 A stout cloth is placed on the bottom of the frame, 

 allowing water to pass through, but retaining the 

 soap. When cool, the sides of the frame are 

 .removed, and the mass of soap cut by means of 

 wires into slabs and bars. 



The oils and fats chiefly used for hard soaps are 

 olive-oil (in France and Italy), tallow, palm-oil, 

 .and coco-nut oil. Coco-nut-oil soap has two peculi- 

 arities which deserve notice : i. It is not easily 

 * salted out,' as it is soluble in solution of salt, un- 

 less this is very strong. It can, therefore, be used 

 for washing in salt water, and is hence called 

 'marine soap.' 2. It can be combined with a 

 very large quantity of water without appearing 

 moist or becoming soft. All hard soap contains 

 water ; but if a manufacturer introduces more than 

 28 or 30 per cent, of water, the adulteration is at 

 once made known by the softness of the soap in 

 all cases where coco-nut oil has not been used. 

 Cases have been observed of soap containing 75 

 per cent, of water and still preserving a tolerably 

 firm character. Such ' dropsical ' soap could not 

 "be sold were it not for the peculiar character of 

 coco-nut oiL 



Rosin Soap or Yellow Soap. Rosin is a mixture 

 of several acids, which form, with soda and with 

 potash, salts resembling soap. They cannot be 

 used alone ; but when mixed with tallow soap or 

 other hard soap, a useful mixture is produced, 

 called yellow or brown soap. The proportion of 

 resin to fat should not exceed 20 or 25 to 100. 



SOFT SOAP is prepared by boiling oil (whale-oil, 

 seal-oil, linseed-oil, or tallow) with solutions of 

 caustic potash. It forms a soft glairy jelly, and 

 contains from 40 to 50 per cent, of water. It is not 

 separated from the lye by means of salt, because 

 double decomposition takes place when salt 

 (chloride of sodium) is mixed with soft soap 

 (oleate, &c. of potash), chloride of potassium and 

 hard soap (oleate, &c. of soda) being formed. A 

 mixture of potash and soda soaps is now exten- 

 sively used as soft soap. It is formed by boiling 

 the tallow or oil with a mixture of caustic potash 

 and caustic soda solution in the proportion of 

 about 4 to i. 



TOILET SOAPS are either ordinary soaps care- 



350 



fully prepared from pure materials, and refined by 

 boiling with salt water, or soaps prepared by mixing 

 almond-oil or lard with cold caustic soda solution. 

 They are perfumed by the addition of some vola- 

 tile oil, such as oil of lavender, bitter almond-oil, 

 &c. 



The detergent action of soap depends upon the 

 fact, that it is partially decomposed by water, 

 caustic alkali being set free. The same property 

 belongs to some other salts of the alkalies, the 

 silicates, for instance ; and a mixture of ordinary 

 soap with silicate of soda (or, for soft soaps, silicate 

 of potash) is now manufactured on a large scale 

 under the name of ' silicated soap.' 



MIXED SOAPS. Many plans have been devised 

 for mixing various substances with soap, with a 

 view to reduce the cost of production. This re- 

 duction is, however, in most cases more than 

 balanced by the reduction in the value of the 

 article ; the additions cost something, and are 

 usually of no use. 



When. soap is mixed with 'hard water,' that is, 

 water containing salts of lime, double decomposi- 

 tion takes place, and an insoluble curdy substance, 

 ' lime soap ' (oleate, &c., of lime), is produced. The 

 waste of soap caused by the use of hard water is 

 therefore proportional to the quantity of lime 

 present in the water. 



ALCOHOL. 



The process of fermentation is described in 

 the paper on CHEMISTRY. We shall here de- 

 scribe the various alcoholic liquids, and explain as 

 far as possible the chemical differences between 

 them. 



WINE is the fermented juice of the grape. The 

 juice of the ripe grape contains water, from 75 to 

 80 per cent ; glucose (grape-sugar), from 10 to 20 

 per cent. ; tartaric acid, partly present as bitartrate 

 of potash, from a half to two per cent. ; albuminous 

 matter, vegetable jelly, and tannin, about one per 

 cent. The colouring-matter of the red wines is 

 derived from the skins. During the fermentation, 

 the glucose is partially transformed into alcohol 

 and carbonic acid. The more completely this 

 change takes place, the ' drier ' is the wine. As 

 already explained (see CHEMISTRY), the presence 

 of the alcohol renders the bitartrate of potash 

 insoluble ; and the more alcohol a wine contains, 

 the less bitartrate can it retain in solution. A 

 weak wine is, therefore, generally a sour wine. 

 The peculiar odour common to all wines is caused 

 by the presence of a volatile ether formed during 

 the fermentation (cenanthic ether) ; the ' bouquet' 

 of the wine, which distinguishes one wine from 

 another, is no doubt due to the presence of various 

 ethers, which, however, occur in such small 

 quantities that their exact nature has not been 

 ascertained. 



To make good wine, the grape-juice should 

 contain at least 20 per cent, of glucose. Now, 

 it frequently happens that grapes otherwise suit- 

 able for making wine do not contain so much 

 sugar, and this defect in sugar is very often ac- 

 companied by an excess of acid, so that the wine 

 produced is both weak and sour. A great deal 

 of controversy has prevailed as to whether a wine- 

 grower is justified in improving artificially the 

 juice of his grapes, so as to produce a wholesome 

 and pleasant drink. We need not here enter into 



