372 MISCELLANEOUS PBODUCTS USED IN AGRICULTURE. XVI. 



In Belgium from 20 to 30 grammes per cubic metre are 

 recommended (i.e., from 2 to 3%).* Considerable difference 

 of opinion appears to exist as to the value of sulphur dioxide 

 as a disinfectant. 



Carbon disulphidc, CS a , the very volatile, inflammable liquid, 

 with the well-known offensive odour, is poisonous both to 

 animals and micro-organisms. Its proposed use as a means of 

 checking nitrification in soils in the autumn has already been 

 alluded to. On combustion it yields carbon dioxide and sul- 

 phur dioxide. With alkaline sulphides it forms thiocarbonates 

 or xanthates (e.g., K 2 CS 8 ), which are sometimes used in treat- 

 ing plant diseases. 



Manganate and permanganate of soda or potash, K. 2 Mn0 4 and 

 KMn0 4 . 



These are powerful oxidising agents, but being non-volatile 

 require to be brought into actual contact with the substance to 

 be oxidised. All oxidisable matter, e.g., nitrites, ferrous salts, 

 organic matter, is first attacked, before the micro-organisms 

 are affected. 



These substances form the active ingredients in " Condy's 

 fluid." 



Zinc chloride, ZnCl. 2 , a deliquescent and caustic white solid, 

 very soluble in water. 



It is a powerful disinfectant. A solution containing about 

 50% of zinc chloride constitutes " Burnett's disinfecting fluid." 

 A more dilute solution is often used in surgery as an antiseptic. 



Carbolic acid, phenol, C, ; H 5 OH, and its homologues, e.g., 

 cresol, C G H 4 (CH 3 ).OH, have long been used as antiseptics and 

 disinfectants. 



They are obtained from coal-tar or from the tar produced by 

 the distillation of wood. 



These substances are poisonous in large quantities and when 

 undiluted are caustic and generally deliquescent. They are 

 only slightly soluble in water, but by the action of alkalies 

 they yield salt-like bodies " carbolates" or " phenates"- 

 which are readily soluble and easily decomposed by acids, 

 even by carbonic acid, yielding again the free phenol. 



Many disinfectants consist of lime or magnesia containing 



* Ricleal, Disinfection and Disinfectants. 



