196 Lintner Soliihle Starch [Dec. 



five liters of distilled water on a Büchner funnel and allowed to dry 

 at 20° C. Two samples of onr own potato starch were prepared 

 in this way. We also washed and dried, in the same manner, two 

 specimens of commercial potato starch. 



2. Preparation of Lintner soluble starch. We prepared 

 Lintner solnble starch from each of the four available specimens of 

 potato starch. Eighty five grams of each product were placed in 

 liter bottles and allowed to stand in 750 c.c. of 7.5 per cent. hydro- 

 chloric acid Solution for seven and one-half days, with occasional 

 shaking. Each product was then washed with 25 liters of distilled 

 water, but despite this treatment the moist starch granules gave an 

 acid reaction when placed on sensitive litmus paper. The samples 

 were then dried for twenty hours in air which was rendered free 

 from dust and fumes. This product dissolved in water at 90° C. 

 with little or no gelatinization. Under the microscope, the product 

 appeared to have the structure of untreated starch. The properties 

 of each product are discussed below. 



Preparation i. From commercial starch {A). We 

 washed the material with 25 liters of distilled water. Wesuspended 

 5 grams of dry commercial starch (A), after the above treatment 

 with acid, in 100 c.c. of cold water and titrated with n/ioo sodium 

 ■hydroxide Solution using rosolic acid as the indicator. The starch 

 showed an acidity equal to the alkalinity of 14 c.c. of n/ioo sodium 

 hydroxide Solution. When samples were suspended in 100 c.c. of 

 water and heated to 40°, 50° and 70°, and then filtered, the filtrates 

 became bright red, purple, and deep blue, respectively, when iodine 

 Solution was added to them. No further attempt was made to wash 

 out the acid. This specimen of soluble starch was subsequently used 

 to show the effects of acid in the preparation of Solutions of Lintner 

 soluble starch. 



Preparation 2. From commercial starch (5). This speci- 

 men of starch (B) was washed with 75 liters of distilled water on a 

 Büchner funnel and was allowed to stand over night in one liter 

 of water treated with i c.c. of ammonium hydroxide Solution of 

 0.90 sp. gr. The product was washed the next day with 25 liters 

 of distilled water and dried as in the case of Preparation i. Five 



