14 BULLETIN 76, U. S. DEPARTMENT OF AGRICULTURE. 



and shows no lumps of gelatinized starch remaining, which should 

 take a little over an hour. The flask is quickly cooled in running 

 water until it can be comfortably handled, then a few drops of methyl 

 orange are added, followed by concentrated ammonia to alkaline reac- 

 tion. Next is added 800 c. c. of 95 per cent alcohol with thorough 

 mixing, and after a few minutes standing to allow air bubbles to sepa- 

 rate, the liquid is strained through moderately coarse muslin. The 

 addition of this amount of alcohol is insufficient to permanently pre- 

 cipitate any starch, but notably thins out the original aqueous solu- 

 tion. Starch will separate some time after the solution has become 

 cold, but with proper management ample time remains for the subse- 

 quent necessary operations. The solution, still at 40° to 45° C, is 

 run through a number of fine jets into 4,000 c. c. of 95 per cent alco- 

 hol, under continuous stirring. The whole is left for at least 48 

 hours with an occasional thorough stirring, after which most of 

 the supernatant alcohol is decanted, and the rest used to transfer the 

 starch to a 2-quart narrow percolator provided with a filter plate 

 which is covered with filter paper or cloth. Here it is percolated 

 with 95 per cent alcohol, being stirred up with a stick at intervals to 

 prevent the formation of clumps or fissures, until the alcohol comes 

 through of a specific gravity indicating a strength of 90 per cent. 

 The starch is then transferred to a Buchner funnel, well drained with 

 suction, and then spread out to dry in a moderately warm place.' 

 The starch so prepared is a fine white powder, more or less compacted 

 to friable lumps, which completely disintegrate under slight pressure. 

 A little of it thrown into cold water in less than a minute dissolves 

 sufficiently to yield a good blue upon the addition of iodin and potas- 

 sium iodid. Moistened with water or diluted alcohol it becomes 

 gummy and dries out to a horny mass, difficultly soluble in cold water. 

 The efficiency of the preparation therefore is dependent upon its 

 fine state of subdivision, and care must be taken during the process not 

 to expose it to air until after thorough digestion with alcohol of 90 per 

 cent strength. It should be passed through a 60 or 80 mesh sieve 

 and protected from moist air. 



The soluble starch may be thoroughly mixed with 10 times its 

 weight of powdered sodium bicarbonate and the mixture divided into 

 powders of about 0.6 gram, which may be packed in a j>aste- 

 board box fitting into compartment B of the case. On the large 

 scale, however, it is much better to make the mixture up into tablets, 1 

 after the following formula : 



1 It is something of an art to make good tablets. No one should attempt it until thoroughly conversant 

 with the principles of the process, and then only on a small scale until experience is gained. 



