graph where sharp changes in the curve occur while the vertical axis of the graph labelled delta t comes from measurement of the voltage generated between thermocouple 24 and thermocouple 30 the horizontal axis temperature is simply measured directly by thermocouple 24 during the heating curve the transformation points of the dta curve will show the solidus and liquidus temperatures of the actual melt 18 in the reactor thus in the sample curves of fig2 transformation point a shows a solidus temperature of 413 degrees c and transformation point b shows a liquidus temperature of 585 degrees c the liquidus temperature of the melt shown is low as compared with a stoichiometric composition because a tellurium rich melt is used specifically to lower the liquidus temperature by varying the te percentage the liquidus temperature of the melt can be roughly selected to be as low as about 400 degrees c non stoichiometric hg rich melts can also be used to attain a lower liquidus temperature but these melts cause a very high vapor pressure of hg thus a sample composition used for the melt would be approximately hg 0 20 cd 0 006 te 0 79 the mercury to cadmium ratio of this mixture is much higher than the 4 to 1 or 5 to 1 ratio which is desired in the final epitaxial layer however incongruent solidification causes the cd to be preferentially deposited as the epitaxial layer is grown of.