No abstract

SummaryThe addition of potassiiim ferrocyanide to the molasses substrate (mash) used in the citric acid fermentation had little or no effect on the total carbon, nitrogen, or phosphorus content of the substrate but reduced the ash content by 1-4% depending on the type and crop year of molasses. Eighteen of the 21 metals identified in beet molasses by spectrographic analysis were precipitated in part by the f,reatment. The metals known to interfere with citric acid production, particularly manganese and iron, were those most efficiently precipitated. At mash temperatures of 80°C. and approximately 100°C., precipitation was completed within 15 min. after ferrocyanide addition and the reductions in the soluble mineral content in each case were similar. At 25OC. the precipitation reactions occurred but required more than 50 hr. to complete. Significantly more total mineral and more iron, calcium, and copper were precipitated at pHs 4 and 6 than at pH 8; manganese precipitation, however, was not affected by these pH changes.

A comprehensive study has been made of the efficiency of copper fluoride as a carrier for the quantitative determination of more than thirty impurities in high purity metallic copper. Although other halides of copper and silver have been shown to improve the sensitivity of their detection, copper fluoride was found to be by far the most versatile and effective. The carrier is added directly to the metallic sample, making the method both simple and unusual. The line intensities of the impurities are apparently independent of the size of the copper sample and dependent only on the quantity of impurities present, a fact which greatly simplifies both calibration and analysis. The limits of detection range down to 10 ppb and are lower than those reported by other spectrographic methods in a number of cases. The results obtained for 15 different elements gave a coefficient of variation of 6.5% on 15 replicate samples. Since extremely pure copper fluoride is vital, a simple method for its preparation is described.

A quantitative spectrographic method has been developed for the determination of traces of iron in high-purity copper and silver. The use of copper chloride as a spectrographic carrier improves the sensitivity and enables the method to be used over a very wide range of concentrations. Samples containing from 0.004 to more than 150 μg of iron (0.07–2500 ppm) can be determined by the identical procedure. A series of 15 replicate copper samples containing 6.4 ppm iron yielded a coefficient of variation of 5.2%. The intensity of the iron spectrum is apparently independent of the copper or silver matrix, which greatly simplifies the preparation of calibration curves. Methods for the preparation of iron-free copper chloride and for purifying graphite electrodes are also outlined.

This study showed that using the atom, ion, and a combination of atom and ion lines of only two elements as internal standards, it was possible to obtain very good results on a wide variety of elements in different matrices The samples were mixed into a rubidium chloride-graphite medium and burned to completion in a dc arc using a Stallwood jet. Analysis of the results, carried out on twelve elements in six matrices, showed that in 55 out of 70 cases an accuracy of better than 15% was attained (29 of these were within 5%). Both major and minor components were determined on the same spectrogram. Elements included Na, Al, Ba, Ca, Fe, Mg, Mn, Pb, Si, Sn, Zn, and Zr with indium and lutecium used as the internal standards.