REAGENTS AND SOLUTIONS 595 



(&) One gram of ^-amino-acetophenon dissolved in 100 c.c. of 

 distilled water and enough hydrochloric acid (about 2 c.c.) added drop 

 by drop, to cause the solution, which is at first yellow, to become entirely 

 colorless. An excess of acid must be avoided. 



Asbestos for Suction Filters. 1 The asbestos is shredded, placed in a 

 wide mouth flask and covered with 10 per cent HC1. Heat on water- 

 bath for five hours. Filter on Buchner funnel, wash free from acid, 

 return to the flask, cover with 5 per cent NaOH and heat on water-bath 

 for three hours. Filter, wash free from alkali, then with dilute acid 

 and finally with water until free from acid. Suspend in a large volume 

 of water, allow to settle for five minutes. Pour off the upper two-thirds 

 and discard. Repeat the washing of the desired coarse portion several 

 times until the supernatant liquid remains nearly clear. 



Bang's Sugar Reagents. 2 (a) Acid KCl Solution. Consisting 

 of 1360 c.c. of saturated KCl to which is added 640 c.c. of water and 

 1.5 c.c. 25 per cent. HC1. 



(b) Stock Copper Solution. Introduce into a 1000 c.c. flask 700 c.c. 

 of boiled and cooled water. Warm to about 3oC. and add 160 grams 

 of pure potassium bicarbonate in powder form. When dissolved and 

 66 grams of pure KCl. Cool and then add 100 grams potassium carbon- 

 ate. Finally add 100 c.c. of 4.4. per cent, solution of pure crystalline 

 copper sulphate. Let stand a short time, then make to mark with 

 boiled water. Allow to stand a day or so before using. 



(c) N/2oo I Solution. Made fresh each day. Dilute N/io I 

 solution 20 times. Or make as follows: Introduce into a 100 c.c. 

 flask 2 grams KI, 1-2 c.c. of 2 per cent KI0 3 solution and 5 c.c. of N/io 

 HC1. Make to mark with boiled and cooled distilled water. 



(d) Starch Solution. A i per cent, solution of Kahlbaum's soluble 

 starch in a saturated KCl solution. 



(e) Dilute Copper Solution. Dilute 300 c.c. of the stock solution 

 to 1000 c.c. Mix with only gentle shaking. Let stand several hours 

 before using. 



BarfoeoVs Solution. 3 Dissolve 4.5 grams of neutral, crystallized 

 copper acetate in 100 c.c. of water and add 1.2 c.c. of 50 per cent acetic 

 acid. 



Baryta Mixture. 4 A mixture consisting of i volume of a saturated 

 solution of barium nitrate and 2 volumes of a saturated solution of 

 barium hydroxide. 



1 See methods entailing use of Gooch crucibles. 



2 Determination of sugar, pages 280 and 524. 



3 Barfoed's test, p. 30. 



4 Isolation of urea from urine, p. 375. 



