DISINFECTANTS AND DISINFECTION 353 



per cent. It is frequently added to beers, cordials, wines and foods (2 to 

 4 grains to the pint) containing sugars. It is also used as a surgical 

 dressing, but other less irritating wound disinfectants are given the 

 preference. 



Crude pyroligneous acid is used as a meat preservative. This acid is 

 obtained by the destructive distillation of wood and contains creosote and 

 other tarry matter and imparts the odor and taste of smoked products. 

 Meats, fish, etc., are immersed in a solution of this acid, dried and sold as 

 smoked. This constitutes the "quick" or "dip" method of smoking 

 meats as compared with the usual slower method of exposing the meats to 

 the smoke of slowly burning wood. 



The following are a few of the less commonly employed preservatives : 

 Fluorine compounds are used in strengths of from 0.03 to 0.02 per cent. 

 Alum is sometimes used in pickling vegetables and meats (brine) because 

 of the hardening effects produced. Copper sulphate is much used in 

 pickling cucumbers, peas, string beans and other green vegetables for the 

 purpose of deepening the green color. Sodium and calcium carbonate are 

 sometimes added to cider and wine to check the souring process (by com- 

 bining with the fruit acids). Formic acid is a powerful preservative. 

 0.014 to 0.08 per cent, retards fermentation. Saccharin, sucrol and dulcin 

 are sweetening as well as preserving agents. Peroxide of hydrogen is used 

 as a preservative. It is also a deodorant. The use of saccharin in food is 

 no longer permissible in the United States. 



6. Insecticides and Other Pest Exterminators 



The farmer, fruitgrower and florist have many enemies belonging to 

 the insecta and to other divisions of the animal kingdom, which interfere 

 with the productiveness of crops. The remedies employed against these 

 pests are numerous. We shall mention only a few of the more useful ones, 

 explaining their action very briefly. They may be grouped into powders, 

 gases, sprays and washes. 



A. Powders. These may be applied by the "pepper box" method, the 

 material being placed in a box, usually of tin, with perforations, through 

 which the powder sifts on shaking. Or a blowing device may be used, 

 like the ordinary bellows box for blowing insect powder, or modifications 

 of this simple device. A third method known as the sifting method is 

 much in vogue in the cotton fields. The powder is placed in a porous bag 

 or cloth, fastened to a stick and shaken over the plants to be treated. 

 Only three powders are used to any considerable extent, as follows: 



a. Slaked Lime. Dry air slaked lime is reduced to a uniformly fine 

 powder which is then ready for use. It is very efficacious with all slimy 

 animals, as slugs and snails. It is applied to plants when the pests are 

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