82 Kansas Academy of Science. 



By prolonged boiling the gelatinizing power is lost. A solution 

 of gelatine placed in the polariscope shows strongly Isevorotary. 



Starch belongs to the cellulose groups of carbohydrates. 

 Carbohydrates are generally understood as being compounds 

 of carbon, hydrogen, and oxygen, the last two elements being 

 present in the proportion in which they occur in water. The 

 cellulose groups (C^HiuO.) include starch, cellulose, dextrin, 

 gums, etc. Pure starch is a glistening, white, granular powder 

 having a peculiar feeling when rubbed between the thumb and 

 finger. It is very hygroscopic, commercial starch containing 

 about 18 per cent of moisture. Starch is very widely dis- 

 tributed in the vegetable kingdom, occurring in almost every 

 plant at some stage in its growth. Starch is insoluble in cold 

 water, alcohol, and ether ; it is soluble in hot water, though not 

 without a change. By boiling with dilute acids, starch is first 

 converted by hydrolysis into a mixture of dextrin and maltose, 

 and finally by prolonged boiling into dextrose. Malt extract 

 also hydrolyzes starch in solution. Though the cereal and 

 vegetable starches, whatever their origin, are identical chemi- 

 cally, the various starch granules have certain characteristics 

 when viewed under the miscroscope that render their identifi- 

 cation easy in most cases. The common starches used in com- 

 mercial food products as pasty materials are wheat, corn, po- 

 tato, rice, tapioca, buckwheat, barley, rye, etc. 



Agar-agar is an important commercial gelatinizing agent. 

 It has an entirely different composition than gelatine. "Agar- 

 agar" is the East-Indian name for seaweed. It is soluble in 

 hot water to a viscid, tasteless, odorless jelly. It is very simi- 

 lar to pectin, but usually considered as gelose (para-arabin — 

 C,;H^„0-). It is thus a carbohydrate. Agar-agar is known by 

 various names, such as Japan agar; Japan, Bengal, Ceylon or 

 Chinese isinglass. True agar-agar is an algae, a species of sea- 

 weed. It is found principally in the Pacific and Indian oceans, 

 and Japan sea. 



Gum tragacanth, an important thickener, is used in such 

 products as ice-cream powders. There are various uses for 

 tragacanth in pharmacy. Gum tragacanth is the gummy ex- 

 udation from Astragulus gummifer. Its habitat is Asia Minor, 

 Syria, and Persia. The derivation of the word is from the 

 Greek "tragos" (goat) and "akantha" (thorn, or horn) ; that 

 is, the exuded gum acquires a horny consistency and appear- 



