260 METHODS OF ANALYSIS [Chap. 



80°C. A small amount of this residue, dissolved in 2 drops of concentrated hydro- 

 chloric acid, should develop a pink color upon the addition of a crystal of resorcin. 

 Evaporate at room temperature the original ether extract of the sample, from 

 which the vanillin has been removed by means of ammonium hydroxid, and dry 

 over sulphuric acid. The residue, if pure coumarin, should melt at approximately 

 67°C. and should respond to Leach's test for coumarin as follows: A small por- 

 tion of the residue, dissolved in not more than 0.5 cc. of hot water, should yield 

 a brown precipitate upon the addition of a few drops of N/10 iodin. This pre- 

 cipitate finally gathers in green flecks, leaving a clear, brown solution. The 

 reaction is especially marked if the reagent is applied with a glass rod to a few 

 drops of the solution on a white plate or tile. 



$ NORMAL LEAD NUMBER'.— TENTATIVE. 



To a 10 cc. aliquot of the filtrate from the lead acetate precipitate, as obtained 

 in 4, add 25 cc. of water, 0.5-1.0 cc. of sulphuric acid, and 100 cc. of 95% alcohol by 

 volume. Let stand overnight, filter on a Gooch crucible, wash with 95% alcohol, 

 dry at a moderate heat, ignite at low redness for 3 minutes, taking care to avoid 

 the reducing flame, and weigh. Conduct a blank determination employing water 

 containing 4 or 5 drops of glacial acetic acid in place of the sample. The normal lead 

 number is calculated by the following formula: 



p ^ 100X0.6831(S-W) ^ ^3^^^ ^^ _ ^^^ .^ ^,^^.^^ 



p = normal lead number (grams of metallic lead in the precipitate obtained 

 from ICO cc. of the sample); 



S = grams of lead sulphate corresponding to 2.5 cc. of the lead acetate solu- 

 tion as determined in a blank analysis; and 



W = grams of lead sulphate obtained in 10 cc. of the filtrate from the lead 

 acetate precipitate, as obtained in 4. 



7 TOTAL SOLIDS.-TENTATIVE. 



Proceed as directed under JX, 4, employing 10 grams of the sample. 



8 ASH.-OFFICL\L. 



Evaporate 10 grams of the extract and determine the ash as directed under 



vin, 4. 



9 ASH CONSTITUENTS.— TENTATIVE. 

 Proceed as directed under III or XXVIII, 21-28, inclusive. 



10 SUCROSE.— TENTATIVE. 

 Determine as directed under VIII, 14 or 18. 



VANILLA RESINS. 



11 Qualitative Test. — Tentative. 



Place 50 cc. of the extract in a glass dish and evaporate the alcohol on a water 

 bath. When the alcohol is removed, make up to about the original volume with 

 hot water. If alkali has not been used in the manufacture of the extract, the resins 

 will appear as a flocculent red to brown residue. Acidify with acetic acid to free 

 the resins from the bases, separating the resins completely and leaving a partly 

 decolorized, clear, supernatant liquid after standing a short time. Collect the 

 resins on a filter, wash with water and reserve the filtrate for further tests. 



