container which when used for thermal analysis is filled with a sample of molten metal the temperature of the molten metal is then recorded in a suitable way the walls of the sample vessel may be coated with a material which reduces the amount of structure modifying agent in the melt in the immediate vicinity of the wall examples of such sample vessels are given in wo 99 28726 and wo 96 23206 the term u201c structure modifying agent u201d as disclosed herein relates to compounds either promoting spheroidization or precipitation of the graphite present in the cast iron suitable compounds can be chosen from the group of inoculating substances well known in the art and shape modifying agents such as magnesium cerium and other rare earth metals the relationship between the concentration of structure modifying agents in molten cast irons and the graphite morphology of solidified cast irons have already been discussed in wo 92 06809 and wo 86 01755 the present invention will be described with reference to the enclosed figures in which fig2 discloses a thermocouple holder which is adapted for containing a thermocouple unit details of the thermocouple unit are shown with broken lines fig3 shows a sampling unit adapted to be used together with and to contain a thermocouple holder and a thermocouple unit details of a thermocouple holder and a thermocouple unit are shown with broken lines in a first aspect the present invention relates to a method for predicting the microstructure in which a certain cast iron melt will solidify the method is based on a known procedure where a sample of a certain cast iron melt.