214 ELEMENTARY AGRICULTURAL CHEMISTRY 



viously moistened with the very inflammable carbon disul- 

 phide. About 1 lb. of sulphur to each 1000 cubic feet of space 

 will probably be the most suitable quantity to use for fumigation. 



Carbon Bisulphide, a very volatile and inflammable liquid 

 of ofiensive odour, gives off a vapour which is very poisonous 

 both to animals and to micro-organisms, but its readiness to 

 catch fire and its explosibility when mixed with air render it 

 too dangerous for use on the large scale. Its temperature of 

 ignition is so low — about 150° C, that a glowing splint or a 

 burning cigarette is suflicient to ignite a mixture of its vapour 

 with air. 



The above are gaseous disinfectants, and are thus readily 

 brought into contact with the material to be disinfected. 

 Many liquid preparations are in use for disinfecting purposes, 

 some of them volatile, and therefore giving oflf disinfecting 

 vapours, 



PAe?zo/, CgH^OH,or*'carbolic acid," and CresoZ,CeH,(CH3)OH, 

 contained in coal-tar or wood-tar, have long been used as dis- 

 infectants. Pure phenol is a colourless, crystalline substance, 

 melting at 41° C. and boiling at 182° C. Often, how^ever, 

 it is used in the form of a liquid (a hydrate), and is soluble 

 in about fifteen times its weight of water. 



With alkalies phenol forms salts, " carbolates," which are 

 much more soluble in water, and are readily decomposed by 

 acids (even by carbonic acid), yielding free phenol again. 

 Many of the " disinfecting " powders of commerce consist of 

 gome indiflferent powder, silica, silicates, or sometimes of lime 

 or magnesia, to which about 15 per cent, of phenol has been 

 added. 



Creasote is a mixture of cresol, CgII^{CH3)0H, xylenol, 

 CgH3 (0112)2011, and other members of this series, and is largely 

 used for preserving timber. 



Lysol is an alkaline (potash) compound of tar oils and fat. 

 It is soluble in water, and owes its disinfecting powers mainly 

 to cresol. 



}\^ood Creasote is obtained from wood - tar, and con- 



