68 TESTING MISCELLANEOUS SUPPLIES. 



10. Glycerin. 



Dissolve 20 to 25 grams of soap in hot water, add a slight excess of sulphuric 

 acid, and heat on a water bath until the fatty acids separate in a clear layer. 

 Remove the fatty acids and filter the acid solution into a graduated flask. 

 Remove the chlorids and the soluble fatty acids by adding crystals of silver 

 sulphate, cool, make up to the mark, mix, allow to settle, filter through dry 

 paper, take an aliquot corresponding to 5 grams of soap, and determine by 

 Hehner's bichromate method (see under Glycerin). This method can not 

 be used when sugar is present as it also would reduce the bichromate. 

 When sugar is present, remove the fatty acids as just described, neutralize an 

 aliquot with milk of lime, evaporate to about 10 cc, add 2 grams of sand and 

 milk of lime containing about 2 grams of calcium hydroxid, and evaporate 

 almost to dryness. Treat the moist residue with 5 cc of 96 per cent alcohol, rub 

 the whole mass into a paste, heat the mixture on a water bath stirring con- 

 stantly, and decant the liquid into a 250 cc flask, wash the residue five or six 

 times with small portions of alcohol, cool the contents of the flask to 15, fill to 

 the mark with 96 per cent alcohol, mix, and filter through a dry paper; evap- 

 orate 200 cc of the filtrate to a sirupy consistency on a water bath, transfer 

 to a stoppered cylinder with 20 cc of absolute alcohol, add three portions of 10 

 cc each of absolute ether, mixing after each addition; let stand until clear, 

 pour off through a filter, and wash the cylinder on the filter with a mixture of 

 two parts of absolute alcohol and three parts of absolute ether. Evaporate to 

 a sirup, dry for one hour at the temperature of boiling water, weigh, ignite, 

 and weigh again. The loss multiplied by 5/4 is the weight of the glycerin in 

 the aliquot taken. Instead of weighing the glycerin it can be titrated after 

 driving off the alcohol and ether. 



11. Sugar. 



Dissolve 5 grams of soap in water, add an excess of hydrochloric acid, heat on 

 a steam bath for thirty minutes, cool, separate the fatty acids, and make up to a 

 definite volume. Add an aliquot, depending upon the amount of sugar supposed 

 to be present, to 50 cc of a mixed Soxhlet solution, make the total volume 

 100 cc, heat to boiling, boil two minutes, filter on a weighed gooch, wash with 

 water, then with alcohol and ether, dry at 100 for thirty minutes, cool, and 

 weigh the cuprous oxid. Calculate the percentage of sugar as invert sugar 

 according to Munson and Walker's tables. 



J. Amer. Chem. Soc., 1906, 28 : 663-686. 

 O 



