198 Lintner Soluhle Starch [Dec. 



50 c.c. of distilled water. In every case these bags were very care- 

 fully tested for defects, and only perfect ones were used.'' 



The dialysis was allowed to proceed for sixteen hours in each 

 case, when portions of each of the four diffusates were siibjected 

 to tests by the reagents with the resiilts indicated below : 



Reducing Chlor in, 

 snbsiance. Silver 



Carhohydrate. Polysaccharid. Fehling nitrate 



Molisch test lodine Solution Solution Solution 



Diffusate f rom Preparation i Strong Bright red Reduction None 



Diflfusate from Preparation 2 Strong Bright red No reduction None 



Diffusate from Preparation 3.... Strong Bright red Reduction (?) None 



Diffusate from Preparation 4 Weaker Bright red No reduction None 



Two gram portions of the soluble starch preparations were then 

 suspended separately in 50 c.c. of cold water and the mixtures 

 allowed to stand for periods of time equal to those of the dialysis 

 treatment in the foregoing experiments. The liquid in each sus- 



' Such bags may be readily prepared by the following method now in general 

 use in this laboratory : Pour into a dry, clean, Erlenmeyer flask (250 c.c. capacity) 

 about 25 c.c. of fairly thick Solution of collodion in alcohol and ether. Gradually 

 pour the sohition back into the bottle containing the collodion supply, but slowly 

 turn the inclined, inverted flask on its longitudinal axis (while the liquid runs 

 out), in Order to effect complete covering of the inner surface of the flask with 

 a layer of the Solution. Keep the inverted flask inclined over the mouth of the 

 bottle of collodion Solution and continuously revolve the flask slowly on its longi- 

 tudinal axis so long as collodion drips from the rim of the flask. Then Surround 

 the upright flask with the hands, in order to warm it, and thus (by favoring 

 evaporation of the solvent) hasten the solidification of the thin, tough, collo- 

 dion lining. 



So soon as the collodion skin on the rim of the flask is dry and stiff (about 

 fifteen minutes after the conclusion of the foregoing process), cut or carefully 

 scrape it off, or loosen it with a finger nail, at that part of the flask, so as to 

 ftiake a free edge at the mouth of the contained collodion bag. Cautiously slip 

 the tip of a knife blade behind the thin delicate membrane in the flask, and allow 

 about 25 c.c. of water to run down between the bag and the flask. Shake the 

 inclined flask gently zvhile it is turned on its longitudinal axis. The membrane 

 can readily be detached from the flask in this manner. If necessary, press the 

 rounded end of a stirring rod against the exterior surface of the bag above any 

 point of special adhesion to the glass. Finally withdraw the detached bag cau- 

 tiously. In pulling on the bag, avoid complete closure of its mouth. Fill the 

 removed bag with water, wipe its exterior dry with Alter paper and determine 

 definitely whether or not the bag leaks. The bag may be translucent and defec- 

 tive if the collodion solvent is not completely eliminated before the treatment 

 with water is begun. (This description of the method of preparing collodion 

 bags is taken from Dr. Gies' niultigraphed directions for laboratory work in 

 physiological chemistry.) 



