Using chemical equations, outline a presumptive test previously used for the detection of nitrates but that has now been abandoned due to false positives resulting in miscarriages of justice. What was the name of the test? What is the resultant colour of the product ion?

Name and outline, with equations, a similar test for nitrates. Which application is the test used for, and why is this test legally safe to use compared to other nitrate tests which have been abandoned?

I was thinking it was the Paraffin Test for the first one but I'm unsure what chemical equations to use.