Part XIX of this International Standard specifies a general method of test for determining the water-soluble nitrates in a sample of pigment by a spectrophotometric method using salicylic acid. Part XIII specifies a method for determining the water-soluble nitrates in a sample of pigment using Nessler's method. NOTES 1 When this general method is applicable to a given pigment, a cross-reference to it will be included in the International Standard relating to that pigment, with a note of any detailed modifications which may be needed in view of the special properties of the pigment in question. Only when this general method is not applicable to a particular pigment will a special method for determination of nitrates be specified. 2 It should be noted that the two methods may not necessarily give the same result, and work is being carried out to compare the two methods.