128 



THE INDIA RUBBER WORLD 



[December 1, 1914. 



14. Barytes. — In the event that the total sulphur is limited 

 by specification, and barytes is permitted as a Idler, the latter 

 must be determined, since the sulphur present in this mineral 

 must be deducted from the total sulphur. The barytes is cal- 

 culated from the barium in the ash determined as follows: 

 Filter off the insoluble matter after the fusion and extraction 

 in par. 13, wash back into the original beaker with hot water, 

 add 5 cc. of 10 per cent, hydrochloric acid, and heat the solution 

 on the steam bath until as much as possible is dissolved. Filter 

 through the same filter as before, washing thoroughly with hot 

 water. Nearly neutralize the solution with sodium carbonate, 

 leaving it slightly acid. Saturate the solution with hydrogen 

 sulphide, and when the lead sulphide has settled filter into a 400- 

 cc. beaker, and wash thoroughly. The total volume should not 

 be over 200 cc. Cover the beaker containing the filtrate, heat to 

 boiling, and add 10 cc. of 10 per cent, sulphuric acid. Allow the 

 precipitate to stand overnight. Filter off the barium sulphate as 

 directed in par. 11. Calculate the percentage of barytes. Then 

 calculate the percentage of sulphur in the barytes by the factor 

 0.1372. 



15. Total Sulphur. — Place 0.5 gram of rubber in a porcelain 

 crucible of about 100 cc. capacity. Add 20 cc. of the nitric acid- 

 bromine mixture (par. 6.), and cover the crucible with a watch 

 glass. Heat very carefully for half an hour to an hour, re- 

 move the cover, rinsing it with a little distilled water, and evapo- 

 rate to dryness. Add 5 grams of fusion mixture (par. 7) and 

 3 to 4 cc. of distilled water. Digest for a few minutes, and 

 then spread the mixture halfway up the side of the crucible to 

 facilitate drying. Dry on a steam bath or hot plate. Fuse the 

 mixture, using a sulphur-free flame, until all the organic matter 

 has been destroyed and the melt is quite soft. Allow to cool, 

 place the crucible in a 600-cc. beaker, and cover with distilled 

 water. Digest 3 or 4 hours on the steam bath. Filter into an 

 800-cc. bealcer. washing thoroughly with hot water. The total 

 volume should be about 500 cc. Add 7 to 8 cc. cone, hydro- 

 chloric acid to the filtrate, and heat on the steam bath. Test the 

 solution for acidity with Congo paper, add 10 cc. 10 per cent, 

 barium chloride solution, and allow to stand overnight Filter 

 off the barium sulphate as before. Calculate to percentage of 

 sulphur present. 



16. Calculations. — 



a. Subtract the "free sulphur" from the "acetone ex- 



tract, uncorrected," and report the difference as 

 t< me extract corrected " 



b. Subtract the sulphur in the ash from the ash as 



determined in par. 12, and report "ash, sulphur- 

 free." 



c. Subtract from the total sulphur determined accord- 



ing to par. 15, the percentage of sulphur present 

 as barytes. if the latter determination has been 

 made (see par. 14), and report the difference as 

 "total sulphur, corrected." Then add the sulphur 

 so deducted to the ash. in this case reporting the 

 latter simply as "ash, corrected." In other words, 

 only the sulphur other than that in barytes will 

 be deducted from the ash when the total sulphur 

 is corrected for barytes. 



d. Subtract from 100 per cent, the sum of the acetone 



extract, corrected, total sulphur (corrected or not 

 as the case may be), and ash (sulphur-free, or 

 corrected for sulphur other than barytes) and call 

 the remainder "rubber by difference." 



e. Divide the acetone extract, corrected, by the sum 

 • if the acetone extract, corrected, and the rubber 

 by difference, and call the result, "ratio, acetone- 

 extract rubber." It will be simpler to express 

 the results in percentages. When new rubber 

 only is used this will give the percentage of 

 acetone-soluble matter in the rubber. 



17. Specific Gravity. — Make this determination in a pyeno- 

 meter, using about 5 grams of rubber cut into small strips, tak- 

 ing care to avoid having air bubbles adhering to the rubber. Do 

 not use a ground sample for this determination, since it is in- 

 tended to determine the specific gravity of the compound as a 

 whole. Aside from the difficulty of completely removing air 

 bubbles, the specific gravity of a sample which is at all porous 

 will be, after grinding, higher than when this is determined on 

 strips. Calculate the specific gravitv on the basis of water at 

 15° C. as 1.00. 



18. Alcoholic Potash. — Fire hose, tested according to the 

 National Board of Fire Underwriters' specifications, calls for 

 an alcoholic-potash extraction. It is performed on the dried 



rubber remaining after the acetone extraction. The complete 

 method will be given under par. 28. 



I! Insulation, 30 Per Cent, Para. 



19. General. — The tests to be made on high-grade insulation 

 compounds are: Acetone extract, unsaponifiable matter, waxy 

 hydrocarbons, free sulphur, ash, and total sulphur, and sometimes 

 alcoholic potash and chloroform extracts. 



20. Acetone Extract. — Determine as under par. 10. 



21. Unsaponifiable Matter. — Add to the acetone extract 

 from par. 20, 50 cc. normal alcoholic potash (par. 5), heat on 

 steam bath under reflux condenser for two hours; remove con- 

 denser and evaporate to dryness. Transfer to separatory funnel, 

 using about 100' cc. water; add 25 cc. ether, and shake. Allow 

 the two layers to separate thoroughly, then draw off the water 

 layer. Continue the extraction of the water layer with fresh 

 portions of ether until the ether will no longer remove any un- 

 saponifiable matter; unite the ethereal layers, and wash with dis- 

 tilled water, adding the first wash water to the extracted aqueous 

 layer. This aqueous solution is reserved for the free-sulihur 

 determination (par. 23), Transfer the ether to a tared Erlen- 

 meyer flask, distill off the ether, dry at 90 to 95°C. ; cool and 

 weigh. 



22. Waxy Hydrocarbons. — To the unsaponifiable matter from 

 par. 21, add 50 cc. absolute alcohol, and heat on the steam bath 

 for one-half hour. Place the flask in a mixture of ice and salt, 

 and let stand for one hour. Filter off the separated waxy hydro- 

 carbons, using S. & S. 589 blue-ribbon filter paper, and applying 

 a gentle suction. Wash with alcohol which has been cooled in 

 an ice-salt mixture. The funnel should be surrounded by a 

 freezing mixture, in order that the temperature may not rise 

 during filtration. Dissolve the precipitate from the filter paper 

 with hot chloroform, catching the solution in a weighed 100 to 

 150 cc. beaker. Wash the flask with hot chloroform and add to 

 the same beaker, in order to include any insoluble matter adher- 

 ing to the walls of the flask. Evaporate off the solvent, dry the 

 residue at 90 to 95° C, cool and weigh. 



23. Free Sulphur. — Transfer the water layer from par. 21 to 

 a 250-cc. beaker, and heat on the steam bath until the ether 

 has been removed. Add 25 cc. bromine water, heat one hour, 

 add 5 cc. cone, hydrochloric acid, and heat until the excess of 

 bromine has been driven off. ( Test for acidity with Congo paper; 

 the amount of acid specified is sufficient if instructions are fol- 

 lowed exactly, and a large excess of acid is to be avoided.) 

 Filter into a' 250-cc. beaker, add 10 cc. 10 per cent, barium 

 chloride solution, and finish the determination as under par. 11. 



24. Ash. — Proceed as under pars. 12 and 13. 



25. Total Sulphur. — Proceed as under par. 15. There will 

 be no correction for barytes. 



26. Calculations. — 



a. Subtract the sum of the free sulphur and waxy 



hydrocarbons from the acetone extract, un- 

 corrected, and report the difference as "acetone 

 extract, corrected." 



b. Subtract from 100 per cent, the sum of the acetone 



extract, corrected, waxy hydrocarbons, ash sul- 

 phur free, and total sulphur, and report the result 

 as "rubber by difference." 



c. Divide the acetone extract, corrected, by the sum of 



the acetone extract, corrected, and the rubber 

 by difference, and report the result under "ratio, 

 acetone extract rubber," as under par. 16e. 



27. Chloroform Extract. — Without removing the acetone 

 from the rubber from par. 20, extract with chloroform for four 

 hours. Evaporate off the solvent in a weighed flask or beaker, 

 dry at 90 to 95° C. cool and weigh. Reserve the rubber for the 

 alcoholic potash determination. 



28. Alcoholic Potash Extract. — Dry the rubber at about 50 

 to 60° C. transfer to a 200-cc. Erlenmeyer flask, add 50 cc. al- 

 coholic potash solution, and heat under a reflux condenser for 

 four hours. Filter through a folded filter into a 250-cc. beaker, 

 washing with 50 cc. of 95 per cent, alcohol, and then 50 cc. of 

 boiling water. Evaporate the filtrate to dryness. Transfer the 

 residue to a separatory funnel, using about 75 cc. of distilled 

 water. Add a few drops of methyl orange, and acidify the solu- 

 tion with 10 per cent, hydrochloric acid. Extract with four por- 

 tions of ether, 25 cc. each, unless the fourth portion should be 

 colored, when the extraction should be continued until no 

 further quantity can be extracted. Unite the ether fractions, 

 wash thoroughlv with distilled water, and evaporate the ether in 

 a weighed beaker. Dry at 90 to 95° C ; cool and weigh. 



