234 ELEMENTARY AGRICULTURAL CHEMISTRY 



applied in dry weather, and care be taken to keep cattle off 

 the treated vegetation. 



Salt. — Hot brine — 1 lb. of salt to 1 gallon of water — is 

 useful for killing weeds on paths, &c. 



Calcium Sulphide (or any soluble sulphide — e.g., fresh gas- 

 lime") is a powerful plant poison. For this purpose it is 

 advisable to use excess of lime, so as to save waste of sulphur. 

 2 lb. of sulphur, 10 to 20 lb. of quicklime, and 10 gallons 

 of water, boiled for an hour or two, are suitable quantities to 

 use. 



Sulphuric Acid. — Oil of vitriol, diluted with about 30 parts 

 of water, will kill weeds. Care must be taken that the acid 

 does not come into contact with iron vessels or be spilt on 

 clothing, &c. 



Carbolic Acid, Phenol. — An ounce of the commercial, acid 

 to a gallon of water will kill plants as well as insects. 



All these substances render the soil barren for some time 

 afterwards. With heavy rains, however, they will soon wash 

 out. Additions of lime to the soil would cure the acidity due 

 to sulphuric acid. 



An example of a differential plant poison is afforded by the 

 so-called " lawn -sand " used for ridding lawns of daisies and 

 plantains. The essential ingredient in lawn sand is sulphate 

 of ammonia, and if it be applied in sufficient quantity — abaut 

 4 oz. per square yard — it will be found that broad-leaved 

 plants, daisies, plantains, &c., are turned brown and killed, 

 while the grasses, though, perhaps, at first slightly injured, 

 soon recover and grow vigorously. 



