THE INDIA RUBBER WORLD 



655 



Samples containing old ground rubber as a filler j-ield, after 

 the second extraction with acetone, a considerable quantity of 

 extract with alcoholic potash solution. It is to be expected that 

 old rubber often will he present in more or less oxidized condi- 

 tion, for which due allowance must be made in interpreting the 

 results. 



METHODS OF ANALYSIS. 



RAPID DETERMINATION OF GOLDEN ANTIMONY IN RUBBER GOODS. 



THE fX)i,Lo\viNG METHOD for the rapid determination of anti- 

 mony sulphide (golden- antimony ) in rubber goods and re- 

 claimed rubbers is that of W. C. Schmitz,' given as translated 

 in the "Journal of the Society of Chemical Industry,'' April 30, 

 1920, page 307.\. 



Two grams of the material is healed with 45 cc. of sulphuric 

 acid in a 300-cc. Kjeldahl flask for 20 minutes; the cooled solu- 

 tion is then treated with 3 grams of ammonium persulphate and 

 gently re-hcated for 10 to 15 minutes longer after it has become 

 colorless. The cooled liquid is diluted, almost neutralized, with 

 ammonia regardless of any precipitate, feebly acidified with hy- 

 drochloric acid, and then saturated with hydrogen sulphide. The 

 precipitate is dissolved in hydrochloric acid containing tartaric 

 acid, and the filtrate, after expulsion of the hydrogen sulphide 

 is titrated with potassium bromate using methyl orange as indi- 

 cator. If the original material contains no iron the precipitation 

 can be omitted ; the colorless solution in sulphuric acid is heated 

 for 20 minutes with 5 grams of potassium sulphate ; a little potas- 

 sium metabisulphite is introduced and the sulphur dioxide ex- 

 pelled by boiling; after repeating this operation twice more the 

 liquid is diluted with 40 cc. of water, and 10 cc. of hydrochloric 

 acid and a considerable quantity of tartaric acid added ; titration 

 is then effected as in the earlier process. The whole estimation 

 needs two to four hours. 



GASOLINE DISTILLATION METHODS.^ 



1. If the electric heater is used it is started and allowed to 

 operate a few minutes first to warm it. 



2. The condenser box is filled with water containing a liberal 

 proportion of cracked ice. 



3. The charge 

 of g a s o li n e is 

 measured into the 

 Engler flask from 

 the 100 cc. gradu- 

 ate. This graduate 

 is used as a re- 

 ceiver for distil- 

 lates without any 

 drying. This pro- 

 cedure eliminates 

 errors due to in- 

 correct scaling of 

 graduates and al- 

 so avoids the cre- 

 ation of an appar- 

 ent distillation loss 

 due to the impos- 

 sibility of draining the gasoline entirely from the graduate. 

 4. The graduate is placed under the lower end of the con- 

 denser tube so that the latter extends downward below the top 

 of the graduate at least one inch. The condenser tube is so bent 

 that the tip can touch the wall of the graduate on the side adja- 

 cent to the condenser box. This detail permits distillates to run 

 down the side of the graduate and avoids disturbance of the 

 meniscus caused by the falling of drops. The graduate is moved 



Technical Paper No. 



Electric G.^siu.ine Distili.atur 



occasionally to permit the operator to ascertain that the speed 

 of distillation is right, as indicated by the rate at which drops 

 fall. The proper rate is from four cc. to five cc. per minute, 

 which is approximately two drops a second. The top of the 

 graduate is covered by a piece of fiber board, the condenser tube 

 passing through an opening. This minimizes evaporation losses 

 due to circulation of air through the graduate and also excludes 

 any water that may drip down the outside of the condenser tube 

 on account of condensation on the ice-cooled condenser box. 



5. A boiling stone (a bit of unglazed porcelain or other porous 

 material ) is dropped into the gasoline in the Engler flask. The 

 thermometer, equipped with a well-fitted cork and with its bulb 

 covered with a thin film of absorbent cotton (preferably the long- 

 fibered variety sold for surgical dressings), is fitted into the 

 flask with the thermometer bulb just below the lower level of 

 the side neck opening. The flask is connected with the con- 

 denser tube. 



6. The electric heater is raised until the flask is in contact 

 with the opening in the top and the gasoline brought to its 

 boiling point. In case it is desired to record the initial boiling 

 point, the thermometer is read when the first drop falls from 

 the end of the condenser tube into the graduate. The amount 

 of heat is then increased so that the distillation proceeds at a 

 rate of from four cc. to five cc. per minute. The thermometer 

 is read as each of the selected percentage marks is reached (20, 

 50 and 90). In case maximum boiling point or dry point (one 

 definition of end point) is to be measured, the heating is con- 

 tinued after the flask bottom has boiled dry until the column 

 of mercury reaches a maximum and then starts to recede con- 

 sistently. 



7. Distillation loss is determined as follows. The condenser 

 tube is allowed to drain for at least five minutes after heat is 

 shut off and a final reading taken of the quantity of distillate 

 collected in the receiving graduate. The distillation flask is re- 

 moved from the condenser and thoroughly cooled as soon as 

 it can be handled. This can be accomplished by using first an 

 air bath and then immersing the bulb of the flask in the ice-water 

 mixture in the condenser trough. The condensed residue is 

 poured into a small graduate or graduated test tube and its vol- 

 ume measured. This residue is retained for the acidity test. The 

 sum of its voluine and the volume collected in the receiving grad- 

 uate, subtracted from 1(X) cc. gives the figure for distillation loss. 

 In case this loss exceeds two per cent, a check distillation should 

 be run to ascertain whether such loss is due to the presence of 

 highly volatile constituents or to failure to condense the lighter 

 fractions on account of too strong heating at the beginning of 

 the distillation. 



SWEET WAX. 



Under the designation "Sweet Wax," a new compounding 

 ingredient is being offered to rubber manufacturers. Its function 

 is to render very smooth running a stock intended for delivery 

 from a tubing machine, and in mold work to impart a highly 

 polished finish to the article. The material also serves as a 

 mild accelerator of vulcanization rather than as a retardant 

 of the cure. 



The material is a blend of hard, waxy hydrocarbons, neutral, 

 of light gravity, and has a yellow to brownish color. 



VULCANIZATION OF RUBBER BY MEANS OF ACCELERATORS. 



J. L. B. Hasselt employs as accelerators combinations of nitro- 

 sodium-ethylaniline with aromatic bases. These accelerators 

 are said to be more active than either constituent alone. For 

 example combinations of two molecules of nitro-sodium-ethyl- 

 aniline may be used with one molecule of each of the following 

 products: aniline, dimethylaniline, o-toluidine, p-phenylene- 

 diamine, x-naphthylamine. 



The amount added to the rubber mixing is from 0.25 to 0.5 

 per cent. ("Le Caoutchouc et la Gutta Pcrcha.") 



