Physical and Chemical Papers. 83 



ance ; or the plant is thorny and the edges of it resist the at- 

 tack of goats. Gum tragacanth is usually found on the market 

 in whitish ribbon-shaped bands, with thorny consistency, and 

 translucent. With fifty parts of water it swells up and forms 

 a cloudy, gelatinous mass. It is principally cellulose, soluble 

 gum, and bassorin acid. 



Dextrin is simply starch heated to 250 C. There are three 

 different kinds of dextrin, which give different chemical color 

 reactions than starch with iodine solution — amylodextrin, 

 erythrodextrin, and achroodextrin. The dextrin principally 

 found in commerce is amylodextrin. Dextrin may also be made 

 from starch by heating starch with dilute mineral acids, or 

 diastase. It is a whitish pow^der, soluble in water. Dextrin 

 has been known to be used as a constituent of certain ice-cream 

 powders. It is sometimes substituted for acacia. 



Gu))i a)'abic or acacia is the gummy exudation from Acacia 

 Senegal. Its habitat is East and West Africa, Arabia, Senegal, 

 Kordofan, Egypt, India, and Nubia. The name comes from 

 the Greek "akakia," a thornj' Egyptian tree, and "ake," mean- 

 ing a point. It is soluble in two parts water, but insoluble in 

 alcohol. Its principal chemical constituents are arabin (arabic 

 acid; gummic acid — Ci,.H..O,,, or Ci„H,^0.) and para-arabin, 

 usually in the form of calcium, magnesium and potassium 

 arabates. 



Albumoi. There are two commercial kinds of albumen — 

 the egg albumen, from white of eggs ; and the blood albumen, 

 from blood serum. Both are soluble in about eight parts of 

 water. Albumen is a nitrogenous compound, and comes in 

 the classification of the single proteins soluble in water and 

 coagulable by heat. For the purpose of this paper, it is not 

 necessary to go into the classification of the proteins. 



Fruit or vegetable pectins. Very little is known about the 

 pectin bodies of fruits and vegetables, but pectin is supposed 

 to be a carbohydrate, similar in its properties to starch. 

 Bracennont, who first investigated pectin, pointed out that 

 he could obtain a gelatinizing agent from alkaline pectates 

 which he isolated from carrots by treating the latter wuth 

 alkalies. He accomplished this in 1825, and made jellies by 

 dissolving these alkaline pectates in water, heating with sugar 

 and then adding a small quantity of mineral acid. In 1909 

 and 1910, Gokhsaite, by the methods of Chodnew and of 



