ASTM D555-84 pdf free.Standard Guide for TestingDrying Oils.
Standards darker than Gardner color No. 18 are notvery useful, since comparison of specimen and standard underthe conditions specified is difficult. When it is necessary tospecify the color of very dark oils,it is usually moresatisfactory to specify the color of the oil diluted with astandard amount of solvent sufficient to bring the color into therange of the standard color-measuring methods.The nature ofthe solvent and the dilution must be specified exactly.
Specific gravity of an oil is a useful measure,sincetranslation from volume to weight,or vice versa，is oftenrequired. For this reason it should be determined with care.Specific gravity is not a measure of the quality of the oil, andan oil that deviates slightly from the specified limits，butotherwise conforms,is usually completely satisfactory.Specific gravity increases with polymerization or oxidation ina regular manner, and for every bodied or blown oil of a givenviscosity there is an appropriate specific gravity.Determine the specific gravity in accordance with TestMethod D 1963,which is capable of high precision and is thereferee method. If less accurate results (3 significant figures)are adequate,”weight-per-gallon”cups as described in TestMethod D 1475 may be used. Specific gravity is very sensitiveto temperature, and the temperature of measurement must becontrolled,or at least known,with high precision. Ifmeasurements are made at other than the standard temperature,or if the value of the specific gravity is required at sometemperature other than the standard,the approximate valuemay be calculated as described in Test Method D 1963.
Refractive index is a scientifically defined property andnumerousaccurate instruments areavailable^for itsdetermination. Since the method used depends upon theinstrument, no method for its determination is given. Any oneof a large number of instruments operated according to themanufacturer’s instructions will give satisfactory results.
Refractive index is not a very useful means ofspecifying drying oils. It is useful in detecting adulteration inoils containing substantial amounts of conjugation，such astung,oiticica,and dehydrated castor oils. Since refractiveindex varies with iodine value，it can be used as a quickapproximation of iodine value.ASTM D555 pdf download.