"microbalance" can estimate "the difference of weight of the order of the millionth of a milligram.".    From Wordnik.com.  [The Breath of Life] Reference

Pregl also contributed a number of micromethods for measuring atomic groups and developed a series of apparatus, including a sensitive microbalance, necessary for his work.    From Wordnik.com.  [Fritz Pregl - Biography] Reference

The XP6U and XP2U ultra-microbalances and the XP6 microbalance with up to 6 g capacity and 0.1 μg or 1 μg readability, provide measurement accuracy, user friendliness, and quality standards.    From Wordnik.com.  [R&D Mag - News] Reference

66Arriving in London, Pettersson had little idea of what he was supposed to work on and Ramsay suggested the construction of a microbalance for his dissertation topic.    From Wordnik.com.  [Trafficking Materials and Gendered Experimental Practices: Radium Research in Early 20th Century Vienna] Reference