18 MAPLE-SAP SIRUP. 



cent alcohol, dry in a water oven, and ignite over a Bunsen burner, applying the 

 heat gradually at first. Cool and weigh. Subtract the increase in weight of lead 

 sulphate from the weight of the blank and multiply by the factor 27. 325. By the 

 use of this factor the lead number is obtained direct without the various calculations 

 required in the original method. 



Determining lead in blank. Transfer 25 cc of the standard lead solution to a 100 cc 

 flask, add a few drops of acetic acid, and make up the whole to the mark with water. 

 Shake, and use 10 cc for the determination of lead as directed in the preceding sec- 

 tion. The use of the acid is imperative" in this case, as it keeps all the lead in solu- 

 tion, when diluted with water, as pure sugar would do. Without its use a negative 

 lead number would be possible, especially if the blank solution were filtered. 



MALIC- ACID VALUE. 



Two methods were employed for this determination, that of the Association of 

 Official Agricultural Chemists, & with a slight modification and the calcium acetate 

 or Cowles method. c 



Association method slightly modified. Weigh 6.7 grams of the sample in a sugar dish 

 and transfer to a 200 cc beaker with 15 cc of water. Add 2 drops of ammonium hydroxid 

 (specific gravity, 0.90); shake, add 1 cc of a 10 per cent solution of calcium chlorid, 

 then 60 cc of 95 per cent alcohol; cover with a watch glass and heat on the steam 

 bath for half an hour. Allow to stand on the steam bath over night with the steam 

 turned off. Filter the material in the beaker through good filter paper and wash the 

 precipitate with hot 75 per cent alcohol until the filtrate measures 100 cc; dry and 

 ignite. Add from 5 to 10 cc of tenth-normal hydrochloric acid to the ignited residue, 

 thoroughly dissolve the lime by heating carefully to just below the boiling point; 

 cool, and titrate the excess of acid with tenth-normal sodium hydroxid, using methyl 

 orange as an indicator. One tenth of the number of cubic centimeters of acid neutral- 

 ized by the ignited residue expresses the malic acid value. Run blanks with each 

 set of determinations, using the same amount of reagents, ammonia, acid, etc., and 

 subtract the result on the blank from the malic acid value obtained. 



Calcium acetate or Cowles method. Weigh 6.7 grams of the sample in a sugar dish. 

 Transfer to a 200 cc beaker with 5 cc of water. Add 2 cc of a 10 per cent calcium 

 acetate solution and shake. Stir in 100 cc of 95 per cent alcohol and agitate the solu- 

 tion until the precipitate settles, leaving the supernatant liquid clear. Filter off the 

 precipitate and wash with 75 cc of 85 per cent alcohol. Dry the filter paper and 

 ignite in a platinum dish. Add 10 cc of tenth-normal hydrochloric acid and warm 

 gently until all the lime dissolves. Cool and titrate back with tenth-normal sodium 

 hydroxid, using methyl orange as an indicator. One- tenth of the number of cubic 

 centimeters of tenth-normal acid is the malic acid number. Run a blank determina- 

 tion as in the other method and subtract the result obtained from the malic acid 

 number. 



TANNIN. 



To 5 cc of a solution of equal parts of maple sirup and water in a test tube add 1 cc 

 of ferric chlorid solution. The iron solution generally floats. Shake a little, a black 

 ring or blackening of solution indicates tannin. 



U. S. Dept. Agr., Bureau of Chemistry Cir. 53. 



& U. S. Dept. Agr., Bureau of Chemistry Bui. 107, Revised, p. 74. 



c J. Amer. Chem. Soc., 1908, 30: 1285. 



