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DIFFERENTIAL THERMAL ANALYSIS APPARATUS DONALD F. APSENEAU Xavier Junior College, Sydney, Nova Scotia, Canada
A LIMITATION of the differential thermal analysis apparatus reported by Hans J. Borchardtl is that it cannot be used to study liquids or substances that melt below 350°C. The sample holders are not always sufficientlytight to prevent leakage of liquids. Present
work2 indicates that the following modification helps overcome this difficulty. I n the figure, A is a rod of the same material as the differential thermal analysis apparatus (brass in this case), machined to fit snugly into the original sample holders. The upper drill hole now becomes the sample holder, while the lower drill hole is provided t o prevent damage to the thermocouples of the apparatus. B shows the differential thermocouple pair which is used t o measure the temperatures within the active and inert materials. They are transite pegs worked to fit tightly into the sample holders and shouldered so that they are inserted to the same depth each time. The thermocouple wires are kept out of contact with the apparatus by being placed in trenches filed in the sides of the pegs and covered with porcelain cement. The tips of the thermocouple probes beyond the transite portion are strengthened by porcelain cement also. C shows a portion of the assembled apparatus ready for the analysis. In the analysis of a liquid or solution, the following procedure yields acceptable results. The sample holders are filled with alumina to a predesigned depth (determined by the length of probe beyond the shoulder), and the liquid is placed on the alumina according to the method of Morita and Rice.a The thermocouple probe is gently inserted into the wetted alumina. In the analysis of fusible solids, the method of Borchardtl is still applicable.
' J. CHEM.EDUC.,33, 103-7 (1956).
'This work was done under a National Research Council Summer Research Associateship, 1957. MORITA,HIROKAZU, AND H. M. RICE,Anal. Chem., 2 7 , 3 3 6 9 (1955).
JOURNAL OF CHEMICAL EDUCATION
