SEARCH:

What happens if gypsum is heated above 700 degree celsius?

 # What happens if gypsum is heated above 700 degree celsius?
A. No by-product
B. Breakdown of CaSO4 which affect gold alloy
C. Breakdown of Na2SO4 which affect gold alloy
D. Gas inclusion porosities

The correct answer is B. Breakdown of CaSO4 which affect gold alloy.

Gypsum-bonded investments are used for casting gold alloys. These can withstand a temperature of 700°C. If gypsum investment is heated about 700°C, decomposition of CaSO4 occurs with emission of SO2 gas. This not only causes shrinkage of the investment but also contaminates the gold castings with the sulphides of the non-noble elements such as silver and copper. So gypsum investments should not be heated above 700°C. 


No comments:

Post a Comment

Add Your Comments or Feedback Here

Subscribe Us: