IRIS. 



G65 



Iodine Reactions. 



With 0.25 per cent Lugol's solution the grains all 

 color a moderate blue-violet (value 55), and the color 

 deepens rapidly until they are deeply colored and have 

 assumed more of a bluish tint. With 0.125 per cent 

 Lugol's solution the grains all color a light blue-violet, 

 and the color deepens rapidly until all the grains are 

 deeply colored. After heating in water until all the 

 grains are completely gelatinized and then treating with 

 a 2 per cent Lugol's solution, the gelatinized grains are 

 all moderately colored and the solution very deeply 

 colored. If the preparation is boiled for 2 minutes and 

 then treated with a 2 per cent Lugol's solution, most of 

 the grain-residues are not colored, except the capsules, 

 but a moderate number are colored a light or a very 

 light indigo; the capsules are all colored violet or reddish 

 violet; and the solution a very deep indigo. 



Aniline Reactions. 



With gentian violet the grains color very lightly to 

 lightly at once, and in 30 minutes they are moderately 

 stained (value 45). There are a few grains which are 

 less colored than the others but most of the grains are 

 moderately stained. 



With safranin, the grains stain very lightly at once, 

 and in 30 minutes they are moderately colored (value 

 50) more than with gentian violet, and practically all 

 the grains are moderately stained. 



Temperature Reactions. 

 The temperature of gelatinization of the majority 

 of the grains is 64° to 66° C, and of all is 68° to 

 70° C, mean 69° C. 



Effects of Various Reagents. 



The reaction with chloral hydrate begins in 1 min- 

 ute. Complete gelatinization occurs in about 6 per cent 

 of the entire number of grains and 12 per cent of the 

 total starch in 5 minutes; in about 16 per cent of the 

 grains and 20 per cent of the total starch in 15 minutes; 

 in about 27 per cent of the grains and 30 per cent of the 

 total starch in 30 minutes; in about 28 per cent of the 

 grains and 36 per cent of the total starch in 45 minutes; 

 in about 30 per cent of the grains and 36 per cent of the 

 total starch in 60 minutes. (Chart D 442.) 



The hilum is very distinct and a bubble is usually 

 formed there. The laniellas are at first indistinct, but 

 later become distinct, especially in the larger grains. 

 The grains become more refractive in appearance after 

 the reaction begins, and the first part to show this is the 

 marginal starch, which forms a narrow and refractive 

 band around the entire grain. Gelatinization begins at 

 small cracks or indentations in the distal margin and 

 the majority of the grains are invaded for some distance 

 through these cracks before the marginal portion be- 

 tween them is gelatinized, so that small, cup-shaped de- 

 pressions are formed in the grain, making the progress of 

 gelatinization somewhat uneven. In this manner, pre- 

 ceded by an increased refractivity but no pitting or 

 granulation of the grain, gelatinization progresses from 

 the distal margin toward the hilum. When the hilum is 

 reached the bubble, usually present there, enlarges, then 

 shrinks and disappears, and as the starch at the proxi- 

 mal end becomes more refractive and somewhat swollen 

 when the hilum enlarges, it also is quickly gelatinized, 

 19 



leaving a small circular portion of the grain just distal 

 to the hilum ungelatinized, and this also is finally gela- 

 tinized. In some of the grains, after the initial crack- 

 ing of the margin and gelatinization at those points, 

 the process extends along the margin between these 

 points until about half of the entire margin of the grain 

 is gelatinized and then proceeds smoothly toward the 

 proximal end. The rest of the reaction is the same as 

 already described. The gelatinized grains are large and 

 considerably distorted, especially at the distal end. They 

 do not retain much resemblance to the form of the 

 untreated grain. 



The reaction with chromic acid begins in 1 minute. 

 Complete gelatinization occurs in about 2 per cent of 

 the entire number of grains and 11 per cent of the total 

 starch in 5 minutes; in about 23 per cent of the grains 

 and 83 per cent of the total starch in 15 minutes; in 

 about 34 per cent of the grains and 91 per cent of the 

 total starch in 30 minutes; in about 51 per cent of the 

 grains and 95 per cent of the total starch in 45 minutes ; 

 in about 74 per cent of the grains and 97 per cent of the 

 total starch in 60 minutes. (Chart D 443.) 



The reaction with pyrogallic acid begins in 30 sec- 

 onds. Complete gelatinization occurs in about 16 per 

 cent of the entire number of grains and 66 per cent of 

 the total starch in 5 minutes; in about 74 per cent of the 

 grains and 98 per cent of the total starch in 15 minutes ; 

 in about 90 per cent of the grains and 99 per cent of the 

 total starch in 30 minutes. (Chart D444.) 



The reaction with nitric acid begins immediately. 

 Complete gelatinization occurs in about 39 per cent of the 

 entire number of grains and 78 per cent of the total 

 starch in 5 minutes; in about 61 per cent of the grains 

 and 95 per cent of the total starch in 15 minutes; in 

 about 82 per cent of the grains and 98 per cent of the 

 total starch in 30 minutes; very little if any further 

 advance in 45 and 60 minutes, respectively. (Chart 

 D 445.) The margin of a small percentage of the grains 

 is quite resistant. 



The reaction with sulphuric acid begins immediately. 

 Complete gelatinization occurs in about 77 per cent of 

 the entire number of grains and 86 per cent of the total 

 starch in 2 minutes; in about 95 per cent of the total 

 starch in 3 minutes ; in about 98 per cent of the grains 

 and in more than 99 per cent of the total starch in 5 

 minutes. (Chart D 446.) 



The reaction with hydrochloric acid begins imme- 

 diately. Complete gelatinization occurs in about 82 per 

 cent of the entire number of grains and 95 per cent of 

 the total starch in 5 minutes; in about 96 per cent of the 

 total starch in 10 minutes; in about 97 per cent of the 

 grains and 99 per cent of the total starch in 15 minutes. 

 (Chart D 447.) 



The hilum is very distinct, and a large bubble is mod- 

 erately often observed to form there, which may vary 

 somewhat in position and first increase slowly in size 

 during the reaction, and later shrink and finally dis- 

 appear. The lamellae are distinct until late in the reac- 

 tion. Gelatinization begins at the hilum which enlarges 

 rapidly. From this point there are two types of pro- 

 cedure to be noted. In the first, which occurs in the 

 great majority of the grains, as the hilum enlarges and 

 the grain swells, moderately fine stria; appear, radiating 

 in all directions from the hilum to the margin, and 



