By means of a toroidal oscillating viscometer logarithmic decrements of dampings have been measured in the presence or absence of HgTl amalgam at 40.1 atomic percent of thallium at different temperatures, ranging from +0.125°C to +15.500°C, with fluctuations every 0.25°C. Measurements were performed in two different periods (1:29/01/1992-14/04/1992 and 2: 18/04/1992-24/09/1992). In both periods, the eutectic was found at 1.125°C. When comparing 40.1% at. Tl, 40% at. Tl and 39.9% at. Tl amalgams, values of the eutectic are perfectly coincident. The logarithmic decrement of the 40.1% at. Tl is located, in the phase diagram, on the left side with respect to the 40% at. Tl.