546 



Annals New York Academy of Sciences 



ference of a wide range of exothermic effects (caused probably by the combus- 

 tion of organic matter). Thermogravimetric analysis was selected because it 

 was thought that the temperature-weight curves of untreated meteorite samples 

 could be meaningfully interpreted even if there was organic matter present. 

 Experiments were performed with the 6 meteorites and with mineral standards, 

 as well as with mineral-organic mixtures. A "Stanton Thermo-recording" 

 instrument was used; the samples were heated in platinum crucibles. The 

 instrument was calibrated for both temperature and weight effects. In addi- 



100 200 300 400 500 600 700 800 900 1000 

 TEMPERATURE, "C. 



100 200 300 400 500 600 700 800 900 1000 

 TEMPERATURE, °C. 



Figure 3. Thermalbalance curves of meteorites (left) and of mineral standards, and 

 of a mineral-organic mixture (right). Heating rate 6.5° C. per minute; each sample weighed 

 0.302 gm. 



tion, standard kaolinite (API-No. 17) and montmorillonite (API-No. 25) 

 samples were run for the purpose of calibration. Each sample was run at a 

 6.5° C. per minute heating rate; sample weights were held identical: 0.302 g. 

 The thermobalance curves are shown in figure 3 (left and right). 



The Orgueil curve shows a gradual decrease in weight to the inflection point 

 (Ai) at approximately 600° C. temperature. At approximately 900° C. there 

 is a second inflection point (Bi). The distillation residue of Orgueil sample 

 (A), heated in an initial vacuum of lO"'^ mm. Hg at 510° C. for a period of 2 

 hours, showed only the effect at Bi . The weight gain in the 400 to 500° C. 

 temperature range may have been caused by the oxidation of magnetite made 

 apparent by the removal of volatile organic matter and part of the water. 



