Abstract: A wavelength calibration solution comprising from about 0.025 to about 0.140 molar neodymium and from about 0.135 to about 0.550 molar samarium, wherein the neodymium is present as a neodymium ionized constituent and the samarium is present as a samarium ionized constituent.A method for checking the wavelength accuracy of spectrometers or spectrophotometers of the type comprising measuring the absorbance (A) or percent transmittance (% T) of a wavelength calibration check solution versus a blank at more than one wavelength. The method is characterized in that the above solution is employed therein as the wavelength calibration check solution.

Abstract: A solution of the type comprising cobalt ammonium sulfate and sulfuric acid. The solution is characterized in that it comprises from about 0.020 to about 0.040 N H.sub.2 SO.sub.4.Also, a method for checking the linearity of response of a spectrometer or spectrophotometer. The method is of the type comprising measuring absorbance (A) or percent transmittance (%T) of a solution versus a blank at a known wavelength. The method is characterized in that the above solution is employed therein.In addition, a method for checking photometric accuracy of a spectrometer or spectrophotometer. The method is of the type comprising measuring A or %T of a solution at a specific wavelength. The method is characterized in that the above solution is employed therein.

Abstract: A method for checking noise of a spectrometer or spectrophotometer. The method is of the type comprising measuring absorbance (A) or percent transmittance (%T) of a solution over a period of time. The method is characterized in that the solution comprises from about 0.040 to about 0.090 M nitrite, the nitrite being present as a nitrite ionized constituent.