In the second half of the 18th century chemists felt the need for greater precision in their experimentation. New, sophisticated scales with hitherto unimaginably small margins of error, favoured the introduction of higher quantitative standards. In addition, the chemists adapted to the needs of their research other gravimetric methods and instruments borrowed from physics, such as the use of aerometers to determine the specific weight of fluids. By using these instruments in combination with pyrometers, the French chemists became leaders in making models of the decimal metric system.