152 METHODS OF ANALYSIS [Chap. 



drop, with constant shaking. If the resultant precipitate is of a reddish color, 

 dissolve it in a few drops of sulphuric acid, and add ferrous sulphate and ammonium 

 hydroxid as before. As soon as a dark colored or greenish precipitate is obtained, 

 introduce 5 cc. of alcohol, dissolve the precipitate in sulphuric acid, shake well and 

 filter. In the absence of abrastol this method gives a colorless or light yellow liquid, 

 while a red color is produced in the presence of 0.01 gram of abrastol. 



35 Sangle-Ferriere Method." 



Boil 200 cc. of the sample with 8 cc. of concentrated hydrochloric acid for an 

 hour in a flask fitted with a reflux condenser. Abrastol is thus converted into beta- 

 naphthol and is detected as directed under 33. 



SUCROL OR DULCIN. 

 QUALITATIVE TESTS. 



36 M or pur go Method.^* 



Evaporate about 100 cc. of the sample, or of the aqueous extract prepared as 

 directed under 1 (C) and neutralized with acetic acid, to a sirupy consistency after 

 the addition of about 5 grams of lead carbonate, and extract the residue several 

 times with 90% alcohol. Evaporate the alcoholic extract to dryness, extract the 

 residue with ether, and allow the ether to evaporate spontaneously in a porcelain 

 dish. Add 2 or 3 drops each of phenol and concentrated sulphuric acid and heat 

 for about 5 minutes on the water bath, cool, transfer to a test tube and overlay with 

 ammonium hydroxid or sodium hydroxid solution with the least possible mixing. 

 The presence of dulcin is indicated by the formation of a blue color at the zone of 

 contact. 



37 Jorissen Method.^^ 



Suspend the residue from the ether extract obtained as directed above in about 

 5 cc. of water; add 2-4 cc. of an approximately 10% solution of mercuric nitrate, 

 and heat for 5-10 minutes on the water bath. In the presence of sucrol a violet blue 

 color is formed, which is changed to a deep violet on the addition of lead peroxid. 



FORMIC ACID. 



Quantitative Method. ^^ 



38 REAGENTS. 



(a) Sodium acetate solution.— Dissolve 50 grams of dry sodium acetate in sufl5- 

 cient water to make 100 cc. and filter. 



(b) Mercuric chlorid reagent. — Dissolve 100 grams of mercuric chlorid and 150 

 grams of sodium chlorid in sufficient water to make 1 liter and filter. 



(C) Tartaric acid. 



(d) Barium carbonate. 



39 APPARATUS. 



The apparatus required (Fig. 6) consists of a steam generator (S), a 300 cc. flask 

 (A) in which the sample is placed, a 500 cc. flask {B), containing a suspension of bari- 

 um carbonate, a spray trap (T), a condenser, and a 1 liter graduated flask (C). 

 The tip of the tube (D), leading into (fi), consists of a bulb containing a number 

 of small holes to break the vapor into small bubbles. 



