Patent ID: 7281394

Claim:
A method of manufacturing a glass substrate for a magnetic disk including a step for chemically strengthening the glass substrate by contacting the glass substrate with chemical strengthening processing liquid containing chemical strengthening salt, wherein the chemical strengthening salt itself contains particles comprising Fe and Cr, the method comprises the steps of: preparing a cleaned chemical strengthening salt comprising Fe and Cr, each of the Fe and Cr having a concentration of 500 ppb or less, wherein the concentration of 500 ppb or less is detected by analyzing a solution obtained by dissolving particles of Fe and Cr captured by a filter into acid by the use of an ICP (Inductively Coupled Plasma) emission spectrometry analyzing method or a fluorescent X-ray spectroscopy analyzing method, and said captured particles are obtained by filtering a solution in which the chemical strengthening salt is dissolved in solvent using the filter, the filter having a minimum capturing particle diameter of 0.2 μm, producing the chemical strengthening processing liquid by the use of the cleaned chemical strengthening salt and, performing a chemical strengthening treatment by contacting the glass substrate with heated chemical strengthening processing liquid.