12 TESTING MISCELLANEOUS SUPPLIES. 



ing point When a sufficient amount of the sample is available, heat one portion 

 to 100 C. and set it aside for the determination of foots, together with a sample 

 Just as it is received. Note also the odor of the warm oil, rubbing it on the 

 hands; a small amount of fish oil may be detected in this way. 



8. Break. 



Heat 50 cc of the oil in a beaker to 300 C. Note whether the oil remains un- 

 changed or " breaks ; " that is, shows clots of a jelly-like consistency. 



9. Moisture and Volatile Matter. 



Heat about 5 grams of oil in an oven at 105 for forty-five minutes ; the loss in 

 weight is considered as moisture. This determination is of course not exact, 

 as there is some oxidation. When a more accurate determination is desired, per- 

 form the whole operation in an atmosphere of hydrogen. 



10. Ash. 



Burn about 20 grams of oil in a porcelain dish and conduct the ashing at as 

 low a temperature as possible. The best oil should contain only a trace of ash. 

 An amount as large as 0.2 per cent would indicate an adulterated or boiled oil. 

 Examine the ash for lead, manganese, and calcium. 



11. Drying on Glass. 



Coat glass plates 3 by 4 inches with the oils to be examined, expose to air 

 and light, and note when the film ceases to be tacky. A good oil should dry to 

 an elastic coherent film in three days. Varying conditions of light, temperature, 

 and moisture have such an influence on drying tests that for comparison of 

 one linseed oil with others all samples must be run at the same time. 



12. Drying on Lead Monoxid. 



Livache's test calls for precipitated lead, but litharge gives equally good 

 results. Spread about 5 grams of litharge over the flat bottom of an aluminum 

 dish 2.5 inches in diameter and five-eighths of an inch high; weigh the dish 

 and the litharge; distribute as evenly as possible over the litharge 0.5 to 0.7 

 gram of the oil, weigh exactly, expose to the air and light for ninety-six hours, 

 weigh again, and calculate the gain in weight to percentage based on the orig- 

 inal weight of the oil used. 



13. Acid Number. 



Weigh 10 grams of oil in a 200 cc Erlenmeyer flask, add 50 cc of neutral 

 alcohol, connect with a reflux air condenser, and heat on a steam bath for half 

 an hour. Remove from the bath, cool, add phenolphthalein, and titrate the 

 free acid with fifth-normal sodium hydroxid. Calculate as the acid number 

 (milligrams of potassium hydroxid to 1 gram of oil). The acid number varies 

 with the age of the oil, and should be less than 8, though when the oil is re- 

 tiiml with sulphuric acid it may show a higher acid number. Test for sul- 

 phuric acid. 



