Materials and Formulas. 163 



liquid within bounds. After standing twenty-four hours the 

 sulphur should be added, and then all the ingredients thoroughly 

 mixed together. The mixture, when dry, should be passed 

 through a sieve having eight meshes to the inch, when it is 

 ready to apply. It has been recommended for various fungous 

 diseases, but is not much used. 



POTASH; POTASSIUM. Various compounds of potash have 

 been recommended for the destruction of insects, but they are 

 not always effective, whether applied at the root or on the 

 foliage. 



Kainit 1 ounce. 



Water 1 pint. 



Other forms may be used in the same manner, but foliage is 

 frequently injured. 

 POTASH SOAP. 



Concentrated lye 1 pound. 



Cotton-seed oil 3 pints. 



Soft water 3 gallons. 



Boil the lye in water until dissolved, then add the oil and 

 boil for two hours, replacing evaporated water with hot water 

 from time to time. Use 1 pound of this soap to 8 or 10 gallons 

 of water on lice-infested plants or trees, and wash the trunks 

 and branches with a stiff brush. 



POTASSIUM SULPHIDE; SULPHURET OF POTASSIUM; LIVER 

 OF SULPHUR; K 2 S. This substance is used when dissolved 

 in water at the rate of to 1 ounce in 1 gallon of water. The 

 solution soon loses its strength, so should be made only just 

 before using. It possesses considerable value in the treatment 

 of certain fungous diseases, as gooseberry mildew, but is not so 

 energetic as the copper compounds. Cost, fifteen to twenty-five 

 cents per pound. 



PYRETHRUM; BUHACH; DALMATIAN INSECT POWDER ; PER- 

 SIAN INSECT POWDER. This powder is obtained from plants 

 of the genus Pyrethrum. It owes its value to the presence of 

 an oil which is exceedingly poisonous to most insects, but appar- 

 ently harmless to the higher animals. The oil acts upon the 

 insect only when in contact with it, in the same manner as 



