148 POWDERED VEGETABLE DRUGS 



The gum arable solution keeps the starch granules in suspension 

 long enough to permit making the counts. Stronger solutions of the 

 gum are not recommended because they interfere with the ready 

 mixing of the substance to be examined and also because they tend to 

 agglutinate the smaller starch granules and proteid granules, thus in- 

 terfering with ready counting. 



Other pure vegetable gums, or egg albumen, may be used in place 

 of the gum arabic in case the latter is not at hand or is not readily 

 obtainable. 



(b) Making the Suspensions. Into a 100 cc. graduated cylinder 

 pour 10 cc. of boiled distilled water, adding thereto 1 gram of the sub- 

 stance to be examined and mix thoroughly by means of a stirring rod 

 and by shaking. The particles clinging to the stirring rod must 

 finally be washed into the suspension. Add 2 per cent, gum arabic 

 solution up to the 100 cc. mark and again mix thoroughly by shaking. 

 The required time and severity of the shaking depends upon the char- 

 acter and nature of the substance to be examined. 



(c) Adding the Iodine Test Solution. After mixing the 1 gram of 

 substance in the 10 cc. of distilled water, add 10 cc. of a 1/10 normal 

 iodine starch test solution and shake thoroughly, then add (to the 

 100 cc. mark) the gum solution as explained in (b). 



The iodine solution is to be used with all substances in which the 

 starch granules may not be very distinct through partial dextrinization 

 or in cases where other particles (fat, oil, proteiad granules, casein, 

 etc.), may interfere with the ready counting of the starch granules. 

 It will be found useful in the examination of cereal flours, dusting 

 powders, pills, tablets, etc. 



(d) Making the Starch Count. Immediately after the final thorough 

 mixing, dip a glass rod into (to a depth to or below the middle of the 

 cylinder) the suspension taking up a droplet which is lightly and quickly 

 touched upon the counting area of the well of a Thoma-Zeiss hemacy- 

 tometer having the ruling of Fuchs and Rosenthal, or that of Turck, or 

 that of Biirker. Spread and mix the droplet upon the counting cham- 

 ber by means of a very slender or pointed glass rod (a pin, using either 

 the point or the edge of the head, is very satisfactory) and place the 

 cover glass in position. 



Substances containing larger starch granules as rye flour, wheat 

 flour, arrowroot starch, potato starch, etc., require the use of the 1/250 

 cmm. areas of the hemacytometer, counting the granules in not less 

 than 25 different areas of the dimension indicated. Careful attention 

 must be given to the starch granules which lie upon or across the ruled 



