Volume 30, Issue 2 (March 2002)
Precision and Relative Bias of Automatic and Manual D 1078 Distillation
ASTM D 1078 Distillation Range of Volatile Organic Liquids is included in the specifications for a number of organic materials used in the paint and related coatings industry, such as hydrocarbon solvents, olefinic solvents, alcohols, ketones, glycols, and esters. Historically, only manual D 1078 distillation has been used. In the last decade, however, the use of automatic distillation has become increasingly prevalent. There are fewer and fewer laboratories that use the manual method. In order to be able to incorporate automatic instruments into the present D 1078, it was necessary to establish the comparative precision and relative bias of the automatic D 1078 procedure to the manual D 1078 procedure. An interlaboratory study was conducted in the summer of 2000 involving six samples of varying distillation ranges, ten laboratories that used automatic instruments, and five laboratories that used manual instruments. The precisions for the initial boiling point, 50% boiling point, and the dry point were found to be dependent on the boiling point temperature. The precision for the distillation range was found to be dependent on the distillation range. Automatic D 1078 distillation results were found to be statistically equivalent to manual D 1078 distillation results. The average relative bias for the six samples included in the study was 0.5°C. ASTM D 1078 has been revised to reflect the new precision value and relative bias of the automatic D 1078 and the manual D 1078 distillation.