352 PHARMACEUTICAL BACTERIOLOGY 



15 per cent, and more is sometimes added to increase the weight. A com- 

 bination of salt and saltpeter is added to meat (brine). The saltpeter 

 gives a red tint to meat besides serving as a preservative. Saltpeter is 

 considered more or less injurious to health, when taken with food to the 

 amount of 0.5 of i per cent, or more. 



Borax and boric acid is often added to milk. 4.4 grains to the pint 

 (0.05 per cent.) keeps milk sweet for a time (10 to 14 hours and longer). 

 Small doses of borax and boric acid (up to i gram per day) is considered 

 harmless. Certain preservatives of a proprietary nature as "Preserving 

 Salts," "Preservative," consist of borax and salt in the proportion of three 

 to one. 



Formalin (the 40 per cent, commercial solution) added to milk, to the 

 amount of 1-50,000, retards souring for several hours; 1-1.0,000 prevents 

 souring for twelve hours and longer, and in this amount it does perhaps 

 very little harm, though it is believed, due to its coagulating effects, to in- 

 terfere with the digestibility of milk ; particularly in children. Several 

 marketed milk preservatives have formalin for their principal ingredient 

 ("milk-sweet," "iceline," "freezine"). 



Sulphurous acid and sulphites are added to vinegar, pickles, catsups, 

 etc., anchovy pastes, canned and dried fruits, etc., to the amounts of 0.2 

 to 1.15 per cent. The part active as a preservative is the available SOz 

 which is gradually oxidized into sulphates. These agents are deodorant, 

 as well as preservative, because of the high oxidizing power. 



Butchers use sulphite preservatives to dust over sausage meats for the 

 double purpose of giving the meat a red color (due to the O combining 

 with the hemaglobin of the blood) and to destroy possible odors of decom- 

 position. 0.05 per cent, of sulphites is sufficient to check decomposition in 

 fresh meats, though the best results follow the use of 0.5 per cent. 0.2 per 

 cent, has germicidal powers when combined with cold. Sometimes 

 aniline color is added to the sausage meat preservatives. 



Sodium benzoate is perhaps the most extensively employed preserva- 

 tive and at the same time the least harmful, o.i per cent, added to food 

 articles, as meats, fruits, catsups, vinegar, cider, etc., checks decomposition. 

 Generally, however, more than o.i per cent, is added, from 0.2 to 0.5 per 

 cent. The percentage of benzoate preservative is likely to vary because 

 of its volatile nature; canners quite generally add an excess knowing that 

 much of it will be carried off with the vapors escaping during the heating 

 process. As a result it follows that products declared to contain o.i per 

 cent, of benzoate may upon chemical examination show the actual amounts 

 to range from a mere trace (0.05 per cent, to 0.5 per cent,). 



Next to benzoate, salicylic acid is perhaps the most common food pre- 

 servative, used much like benzoate, in strengths varying from .01 to 0.25 



