184 PHARMACEUTICAL BACTERIOLOGY. 



paraffin or soluble silicate, which exclude the air, or they may be preserved 

 in brine, salt or other so-called harmless chemical preservative. 



Herring, cod and other fish are often preserved in a brine of salt or of equal 

 parts of salt and borax or boric acid. Of meats, fish is particularly liable 

 to decomposition and it is declared that certain kinds cannot be preserved 

 in salt alone, that it is necessary to add boric acid, rubbing the preservative 

 well into incisions made along the spinal column where the decomposition 

 develops earliest. Salt is used with meats generally and with butter. Two 

 per cent, of salt in butter is sufficient, though as much as 15 per cent, and 

 more is sometimes added to increase the weight. A combination 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 in- 

 jurious 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," " Pre- 

 servative," 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; i-i 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 interfere 

 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 SO 2 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 percent. 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 preservative 

 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. Gen- 

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



