CHAMBERS'S INFORMATION FOR THE PEOPLE. 



nettle. To take another example, common fousel 

 oil (see p. 306) consists mainly of an oily liquid, to 

 which the name ' amylic alcohol ' has been given. 

 This substance has the composition C 8 H 12 O (or 

 C 5 H n O H) ; it yields water and a compound 

 ether when treated with an acid, for instance : 



C 5 Hu O H + HC1 = H-O-H + C 6 H^Cl 



Amylic Alcohol. Hydrochloric Water. Chloride of 



Acid. Amyl. 



When oxidised by means of a mixture of sulphuric 

 acid and bichromate of potash, it is converted by 

 the loss of two atoms of hydrogen into C 5 H 10 O, 

 which is easily oxidised to valerianic acid, C 6 H 10 O 2 , 

 an acid also obtained from the plant ' valerian,' 

 whence its name. 



Polyatomic Alcohols and their Derivatives. 

 Chloride of methyl, which is the hydrochloric 

 ether of methylic alcohol, can also be obtained 

 by the action of chlorine upon marsh gas (CH 4 

 + C1 2 = CH 3 C1 + HC1); and similarly, the chlo- 

 ride of ethyl, the chloride of amyl, &c. can be 

 obtained by the action of chlorine upon the cor- 

 responding hydrocarbons, C 2 H 6 ; C 5 H 12 ; &c. We 

 have thus a relation between the class of alco- 

 hols which we have just been considering, and 

 compounds of carbon, hydrogen, and one atom 

 of chlorine. Now there are other classes of alco- 

 hols which stand in a similar relation to certain 

 compounds of carbon and hydrogen with two or 

 more atoms of chlorine. It will be sufficient for 

 our present purpose to give a few examples of 

 such alcohols. Olefiant gas (see p. 324) unites 

 with its own volume of chlorine gas to form a 

 colourless volatile liquid, sparingly soluble in 

 water, called chloride of ethylene, or ' oil of Dutch 

 chemists,' because it was discovered by four 

 Dutch chemists. This substance has the formula 

 C,H 4 C1 2 , and is formed by the union of C 2 H 4 and 

 Clfr It has many points of analogy with such a 

 metallic chloride as chloride of lead, PbCl 2 , just 

 as chloride of ethyl resembles in many respects 

 chloride of sodium, NaCL Thus, if chloride of 

 lead is treated with acetate of silver, we get 

 chloride of silver and acetate of lead ; and similarly, 

 chloride of ethylene with acetate of silver gives us 

 chloride of silver and acetate of ethylene ; and by 

 acting on acetate of ethylene with caustic potash, 

 we obtain acetate of potash and hydrated oxide of 

 ethylene ; just as acetate of lead and caustic potash 

 yield acetate of potash and hydrated oxide of lead. 

 Hydrated oxide of lead is H O Pb O H, and 

 hydrated oxide of ethylene is H O C 2 H 4 O H. 

 Here ethylene (C 2 H 4 ) is a dyad radical, and its 

 hydrated oxide (which, from its sweet taste, has 

 been called glycol) is a diatomic alcohoL Glycol 



CoH. 



OH 



OH 

 Glycerine. 



H-C 2 H 3 S 



Acetic Acid. 



forms compound ethers with acids, and just as in 

 the case of lead we have normal and basic salts, so 

 from glycol we can obtain normal and basic ethers ; 

 CjHiCLj or Cl C 2 H 4 Cl, and H O C 2 H 4 Cl 

 may be given as examples. When oxidised, 

 glycol yields, among other products, its aldehyd, 

 'glyoxal' (C 2 H 2 O 2 =C 2 H 6 O 2 2H 2 ), which is easily 

 oxidised to form oxalic acid, C 2 H 2 O 4 . Oxalic acid 

 is a white crystalline solid, readily soluble in water. 

 As crystallised from its aqueous solution, it con- 

 tains two molecules of water of crystallisation. It 

 has an intensely sour taste, and is very poisonous. 

 It is produced in the oxidation of very many 

 organic substances ; thus, when sugar is boiled with 

 nitric acid, much oxalic acid is formed. It is now 

 usually prepared by heating sawdust (impure 

 cellulose) with caustic potash hydrogen is given 

 off, and oxalate of potash (C 2 K2O 4 ) formed ; from, 

 this, oxalic acid can be obtained. Oxalic acid is a 

 dibasic acid (see p. 317). Its most important salts 

 are : Acid oxalate (binoxalate) of potash, or ' salt 

 of sorrel,' C 2 HKO 4 , which occurs in the juice of 

 various kinds of sorrel ; oxalate of lime (C 2 CaO 4 ). 

 Glycerine, a substance of great importance, the 

 preparation of which will be described presently, 

 is an example of a triatomic alcohol. Its formula is 



, O H 



C 3 H 8 3 orC 3 H 5 -0-H 

 ' O H 



Here the radical C 3 H 6 is triad, like bismuth in 

 Bi(OH) 3 . Accordingly, glycerine forms with acids 

 compound ethers, of which there are three series, 

 which we may represent by the examples C 3 H 6 Cl3, 

 C 3 H 5 C1 2 (OH), and C 3 H S C1(OH) 2 . Erythromannite, 

 a sweet substance obtained from certain lichens, 

 is an example of a tetratomic alcohol (C 4 H 10 O 4 

 or C 4 H 6 (OH) 4 ) ; and mannite, a sweet crystalline 

 substance found along with sugar in the manna, 

 or sweet exudation from the ash-tree, is an example 

 of a hexatomic alcohol The formula of mannite 

 is C 6 H 14 O 6 (or C 6 H 8 (OH) 6 ), and differs from that 

 of grape-sugar by containing two atoms of hy- 

 drogen more ; and grape-sugar (especially levulose, 

 p. 332) can be converted into mannite by treating 

 it with nascent hydrogen. 



FATS AND OILS. 



Soap. If pure acetic acid and glycerine be 

 mixed together and heated, the product will be 

 found to be different according to the temperature 

 and the proportion in which the two substances 

 are mixed. If the temperature does not rise 

 above 212 F. the reaction takes place in accord- 

 ance with the equation : 



H O H 



Water. 



C 2 H 3 O r 

 C.HJOH. 

 (OH. 



Monoacetine. 



If sufficient acetic acid is present, and the tern- action of exactly the same kind takes place, 



perature is raised to 480 



OH 

 OH 

 OH 



Glycerine. 



F. a more complete 



H C 2 H 3 2 

 H-C 2 H 3 2 

 H-C 2 H 3 0, 



Acetic Acid. 



thus: 



H O H 

 H O H 

 H O H 



Water. 



C 3 H 5 



CHO 



3a . 



C 2 H 3 2 . 



Triacetine. 



When the conditions are intermediate, diacetine 

 C 2 H 3 2 x 



C,H 3 O 2 I is formed. 

 . OH / 



334 



Monoacetine and diacetine are basic compound 



ethers of glycerine ; while triacetine is a normal 



I compound ether. Now, the fats and fixed or 



I greasy oils, which are found in such abundance in 



