60 TESTING MISCELLANEOUS SUPPLIES. 



tory funnel, add dilute sulphuric acid (1:3) until the liquid is distinctly acid 

 to litmus, cool, shake with ether, drain off the acid layer and shake it twice 

 with additional portions of ether, wash the ether twice with water, unite the 

 acid water solutions, transfer to a large round-bottomed flask, and render dis- 

 tinctly alkaline with sodium hydroxid, but avoid a great excess of alkali, as 

 it will cause foaming. Use a spray trap and a large condenser. In all dis- 

 tillations tie the stopper in the flasks and condensers, as they are liable to be 

 blown out, and distil in a current of steam until all of the pyridin has passed 

 over. This is usually a tedious operation, but in most cases the pyridin can 

 be driven over in the first 600 or 700 cc. To ascertain whether all of the 

 pyridin has come over, mix 10 cc of the distillate with 10 cc of a solution of 

 1 drop of half-normal sulphuric acid in 50 cc of water colored with methyl 

 orange. The 10 cc of distillate should not change the color of the solution. 

 Transfer the distillate to a 1,000 cc graduated flask, add an excess of half- 

 normal sulphuric acid, fill to the mark, mix, and titrate aliquots back with fifth- 

 normal sodium hydroxid using methyl orange. From the amount of half- 

 normal sulphuric acid neutralized, calculate the percentage of pyridin (1 cc of 

 half -normal sulphuric acid corresponds to 0.0395 grain of pyridin). 



3. Heavy Hydrocarbons. 



The ethereal layer above the acid solution in which the pyridin is, contains 

 hydrocarbons, phenols, and fatty and resin acids. Add a 25 per cent solution 

 of sodium hydroxid in amount sufficient to combine with all the fatty and resin 

 acids and phenols, shake, add water to dissolve the soaps, shake again and 

 allow to settle. It will frequently be observed that there are not two layers, 

 but three, and care must be taken to distinguish between the dark ethereal 

 layer and the intermediate dark alkaline layer below it. Draw off the liquid 

 underneath the ether, shake out twice again with ether, wash all ether por- 

 tions three times with water, unite the ether solutions in a weighed Erlenmeyer 

 flask, distil off the ether, dry for three-quarters of an hour on a steam bath, 

 wipe out the moisture from the neck of the flask, and weigh as heavy hydro- 

 carbons. Concordant results can not be obtained by drying to constant weight, 

 hence it is always much better to leave the Erlenmeyer flask on the steam bath 

 exactly three-quarters of an hour after distilling off the ether. 



4. Phenols. 



Heat the alkaline liquid separated from the heavy hydrocarbons on the steam 

 bath to drive off the ether, transfer it to a round-bottomed flask, make distinctly 

 acid with sulphuric acid (1:3) and distil in a current of steam until no more 

 oily drops pass over (do not use a spray trap) ; to the distillate add an excess 

 of sodium hydroxid, evaporate to about 20 cc, transfer to a narrow graduated 

 MopiK-n-d rviimi.T. acidify with sulphuric acid (1:3) keeping it cool, mix, 

 allow to settle over night, and measure the layer of phenol. The volume in 

 cubic centimeters multiplied by 1.05 gives the number of grams of phenols. 



5. Fatty and Resin Acids. 



Cool thr n-siihn- in a distilling flask, extract with ether, distil off the ether. 

 dry on u steam bath tlirc<- -quarters of an hour, cool, and weigh as fatty and 

 resin acids. 



