INCIDENTAL PRODUCTS 291 



are great possibilities. There are produced every year 

 millions of gallons of cider, immense quantities of jelly 

 from apple peelings, prussic acid from apricot pits, alcohol 

 from waste products such as worthless potatoes and fruit 

 pulp, marmalade from cull oranges, citric acid and lemon 

 flavoring extract from cull lemons, sirup, oil, extract of 

 tannin, and raisin-seed meal from raisins, and many other 

 by-products. A few years ago these would have been dis- 

 carded as worthless, yet now their value runs into millions 

 of dollars annually. The instructive and interesting feature, 

 however, is that the present number of horticultural by- 

 products represents a beginning only. The annual losses are 

 still immense; each loss is a challenge to the intelligence of 

 the trained horticulturists of America, and as time goes on 

 new by-products will be constantly added to the list. 



404. Vinegar manufacture. Apple cider contains a cer- 

 tain amount of sugar, which, if unmolested for a brief time, 

 changes into alcohol. This change is brought about by the 

 action of bacteria on the sugar. The alcohol in turn is 

 transformed into acetic acid by another set of bacteria. 

 Although other substances besides acetic acid are pres- 

 ent in commercial vinegar, acid is the essential in the final 

 product. 



If home-made vinegar is examined closely, a scum will be 

 seen over the top of the mass, a dark-colored substance which 

 is commonly known as " mother of vinegar." This mass is 

 nothing more nor less than a collection of large quantities of 

 the acetic-acid-forming bacteria ; and whenever a new lot of 

 cider is to be changed to vinegar, the process is hastened by 

 adding some of the " mother" to it. 



Several species of bacteria have the power of changing 

 alcohol into acetic acid, all of them differing slightly in regard 

 to conditions under which they live. Since some of these 

 species are better than others, the makers of vinegar are at 

 present endeavoring to sort out the more favorable types to 



