LUBRICATING OILS. 57 



3. Ash. 



Char carefully 10 grams of the sample in a 100 cc, or larger, platinum dish, 

 extract with water, filter, burn filter and carbonaceous matter, add water 

 extract, evaporate, and heat to low red heat. 



4. Borax. 



To 30 grams of the sample in a large platinum dish add 5 cc of a 20 per 

 cent solution of sodium hydroxid and 10 cc of a saturated solution of barium 

 hydroxid, char, extract with water and dilute hydrochloric acid, ash the resi- 

 due, and extract the ash with dilute hydrochloric acid. Transfer to a 250 cc 

 graduated flask, add about 0.5 gram of calcium chlorid and a few drops of 

 phenolphthalein, then a 10 per cent solution of sodium hydroxid until slightly 

 alkaline, followed by 25 cc of lime water. Make up to mark, mix, filter through 

 a dry paper and titrate 100 cc, with half-normal sulphuric acid until the pink 

 color disappears, then add methyl orange and continue the addition of half- 

 normal sulphuric acid until the yellow is changed to pink. Add fifth-normal 

 sodium hydroxid until the solution is exactly neutral to methyl orange; boil 

 until all carbon dioxid is driven off, cool, add almost enough mannite to satu- 

 rate the solution. Add phenolphthalein and titrate with fifth-normal sodium 

 hydroxid. 



One cubic centimeter of fifth-normal sodium hydroxid corresponds to 0.0191 

 gram Na 2 B 4 O T 10H 2 O ; 0.0101 gram Na 2 B 4 O 7 ; 0.0124 gram H 3 BO 8 ; 0.007 gram B 2 O 8 . 



5. Gelatin. 



Determine the nitrogen and multiply by 5.56. From the moisture and gelatin, 

 if these values are known for the glue originally used, an approximation of 

 the amount of glue used in making the pad can be calculated. The ash is 

 only a rough check, as some of the boric acid is lost on burning. 



LUBRICATING OILS. 



1. Specific Gravity. 

 Determine in the regular manner, see pages 7 to 10. 



2. Flash and Fire Points. 



Follow the method given under linseed oil, page 11. 



3. Viscosity. 



Strain the oil through bolting cloth and determine the viscosity by the Engler- 

 Ubbelohde method." Great care should be taken to have the apparatus thor- 

 oughly clean, and the temperature of the oil must not vary. 



4. Ash. 



Burn 10 grams of the oil at as low a temperature as possible, using a quartz 

 or porcelain dish. (Do not use platinum, as some lubricating oils contain lead 

 soaps.) Determine the reaction of the ash with litmus paper. The amount of 

 ash should be very small and neutral unless the oil contains soap, when the 

 reaction will be alkaline, unless it is a lead soap. 



Ubbelohde, Handbuch der Oele und Fette, 1 : 341. 



