Estimation of the molecular weight of horse serum albumin from the osmotic pressure of solutions containing 0.713 to 5.12 gm. per 100 cc. shows that the Hepp osmometer yields the same values as the standard simple osmometer of Adair.
Accuracy and precision of the instrument decrease noticeably at concentrations of albumin less than 0.7 gm. per 100 cc.
A determination in duplicate can be carried out with this instrument in less than 2 hours.
The instrument is easily operated.