本文报导一个在pH2.5-3.5显色的亚硝基-R盐测钴方法,使用了前人未用过的磷酸二氢钾作缓冲剂和络合剂。旧法的显色酸度为pH2.5-8,我们的试验证明在磷酸二氢钾介质中对纯钴这一结论也是成立的。但当钴和铁共存时,能得到最大吸光度并保持稳定的显色pH范围是2-4。因为pH>4后,磷酸铁络合物已不太稳定,由于析出的氢氧化铁沉淀吸附钴,致使吸光度随pH的增高而递减。众所周知,铜、镍等的干扰可提高介质酸度消除之。因此,选用较低的pH显色,先行抑制这些干扰元素 This article reports a method for the colorimetric nitroso-R measurement of cobalt at pH 2.5-3.5 using previously unused potassium dihydrogen phosphate as a buffer and complexing agent. The colorimetric acidity of the old method is pH 2.5-8, and our test proves that the conclusion of pure cobalt in potassium dihydrogen phosphate medium is also true. However, when cobalt and iron coexist, the maximum color-developing pH range that gives the maximum absorbance and remains stable is 2-4. Because pH> 4, the iron phosphate complex has been less stable, due to precipitation of iron hydroxide precipitate cobalt adsorption, resulting in the decrease of absorbance with increasing pH. As we all know, copper, nickel and other interference can increase the medium acidity elimination. Therefore, the choice of low pH color, first inhibit these interfering elements