INDEX 



469 



Water (Cont.) : 



potable, 13 



purification of water supplies, 15 



re(|uirement in humans, 12 



softening, 15-17 

 Wax alcohols, 91, 93 

 Wax esters. 92 

 Waxes, natural : 



biological role, 92 



composition of, 92-94 



occurrence, 92 



properties of, 92 

 Weed killers, 407 

 Weight reduction : 



by muscular activity, 429 



principles of, 429 

 Work, relation to free energy changes, 414 



X 



Xanthine : 



formula of, 154 



metabolism of, 155 



oxidases, 268 

 Xanthophyll, 84. 205, 209 

 Xanthoiiroteic test, 142 

 Xerophthalmia, 203, 205 

 Xylan, 51 



Xylitol, 21 



Xylosazone crystals, 47 

 D-Xvlose, 20 

 L-Xylulose, 27, 28 



Yeast, production, 361. 371 

 Yellow enzymes, 140 



Zeaxanthine, 205 



Zein, 108, 126 



Zeolites. 16, 17 



Zinc : 



biological role, 189-101 



in carbonic anhydrase, 187, 189 



content in average diet, 191 



content of food, table, 442 



food sources of, 191 



in fertile soils, 191 



in insulin, 301 



Zinc deficienc.v, effect on plants, 191 



Zinc oleate, 88 



Zinc stearate, 88 



Zwitterion, 97 



Zymogenic cells, 312 



Zymogens, 273 



