SPECIAL INDUSTRIAL FERMENTED PRODUCTS 653 



recently were largely an economic loss. Through the investigations 

 of Dr. E. M. Chace and C. P. Wilson of the United States Bureau of 

 Chemistry, a commercially stable citric acid industry has been founded 

 in California. The plant of the Exchange By-Products Companv 

 at Corona is capable of caring for over 100 tons of fruit per day. 

 The lemons are first peeled in special rotary grating machines. The 

 peels are distilled to recover the essential oil. The peeled fruit is 

 crushed and pressed in powerful continuous presses. The juice is 

 pumped into vats of about 30,000 gallons each where it is permitted 

 to undergo spontaneous alcoholic fermentation. The purpose of the 

 fermentation is to destroy the slimy nature of the juice, making it 

 possible to filter the fermented juice easily. The fermented juice is 

 filter pressed; the clear liquid is neutralized with calcium carbonate 

 at the boiling point because calcium citrate is more insoluble in hot 

 than in cold liquids; the calcium citrate is removed by filtration, treated 

 with sulphuric acid in slight excess, the calcium sulphate is removed 

 by filtration, the citric acid filtrate is partially concentrated in open 

 vats by a stream of air, concentrated to the crystallizing point in 

 glass-lined vacuum pans, is allowed to crystallize in shallow vats, 

 the crude crystals are redissolved in water, and recrystallized to give 

 citric acid of commerce. The manufacture of this product has done 

 much to stabilize the lemon growing industry in California. 



It is stated that it is possible by means of pure cultures of certain 

 varieties of citromyces (a penicillium-like mold) if a 5 per cent, sugar 

 solution is used, to convert 50 per cent, of maltose, 30 per cent, of 

 sucrose, 5 per cent, of arabinose, and 24 to 29 per cent, of glycerol into 

 citric acid. Wehmer states that citromyces cultures may be easily ob- 

 tained by exposing a 2 to 5 per cent, solution of citric acid and cane 

 sugar to the air for several weeks. These cultures may be used to 

 convert dilute cane sugar solutions containing a small amount of 

 ammonium nitrate, dipotassium hydrogen phosphate and magnesium 

 sulphate into dilute solutions of citric acid which may be safely used as 

 lemonade or a source of citric acid. As high as a 4 per cent, citric 

 acid solution may be readily attained at 18 to 25 in 8 to 14 days. 

 If left too long the acid is oxidized and the liquid in time becomes 

 neutral or alkaline. If calcium carbonate is added before inoculation, 

 higher yields of acid are obtained. Above 25 growth is inhibited with 

 many strains of citromyces, 



