BAKINC POWDBB AND P-AKIN-: ( ' ! I KM ICALS. 171 



(b) METHOD USING HEIDENHAIN'S APPARATUS. 



(1) DESCRIPTION OP APPARATUS. 



This apparatus was originated by G. J. Mulder, recommended and Improved 

 by Kolbe, Stolba, and Fresenius," and modified by H. Heidenhain.a As shown in 

 fit:. 1<>. drawn on a scale of 1 : 12, it consists of 



A A < ylinder filled with soda lime to free the air from carbon dioxid. A 

 thick layer of cotton prevents soda-lime dust from being carried over. 



B. Glass cock to regulate the air current, which finds resistance at C. 



('. A capillary contraction. 



D. Funnel tube of peculiar shape. The funnel is cylindrical, three-fourths of 

 an inch wide and 4 inches long, and is reduced to half its width at the bottom, 

 so as to make a neck for a perforated rubber stopper. 



E..A glass tube is tightly fitted into the perforated rubber stopper, allowing 

 the stopper to be taken out and replaced by the glass tube. 



F. Evolution flask, ordinarily of 150 cc capacity, for foaming liquids of 300 cc 

 capacity. 



G. Return condenser, simply a glass tube of one-fourth of an inch bore, 

 around which a small lead pipe is wound. The tube following the condenser 

 contains a few pieces of calcium chlorid to retain the bulk of the moisture. It 

 is refilled when contents are liquefied. 



H. U tube filled with coarse calcium chlorid. 



K. Filled at I with a 3-inch long column of pumice stone impregnated with 

 copper sulphate completely dehydrated at 150 C. The remainder of the tube 

 Is filled with fine calcium chlorid. 

 L. Cock to close the apparatus when not in use. 



M. First absorption tube about one-half inch in diameter and 5 inches long, 

 filled mainly with soda lime, with a little calcium chlorid at the side at which 

 the air current enters. 



N. Second absorption tube of same size as M, filled half with soda lime and 

 half with calcium chlorid. Place the side containing calcium chlorid toward 

 the end of the apparatus where the air current leaves. 



JP. Guard tube containing calcium chlorid toward N and soda lime toward P. 

 '. Indicator tube trapped with glycerin. 



Safety bottle to receive water which may be sucked back from the 

 irator. 

 The aspirator, which is a Mariette's bottle of about 4 liters capacity. 



'(2) PREPARATION OF REAGENTS. 



Use calcium chlorid dehydrated at 200 C., not fused. Grind it coarsely in 

 coffee mill and sift through No. 18 wire gauze to remove the extremely 

 arse and through No. 30 wire gauze to remove the very fine. Prepare a large 

 lantity of such calcium chlorid at the beginning and use this for the tubes 

 M. and N. The reason for this is that the current of air must leave the 

 ghed tubes with the same content of moisture as it entered them, which 

 nly can be attained if the absorbent in K and N is of the same nature and 

 juality. 

 Grind and sift the soda limec for the weighed tubes in the same way. It 



Fresenius, Quantitative Analysis. 1:14!>; 2:308, German edition. 

 6 J. Amer. Chem. Soc., 1896, 18 : 1. 



" An excellent method for the preparation of soda lime is given by Benedict and Tower, 

 Amer. Chem. Soc., 1899, 21 : 396. 



87404 Bull. 10700 13 



