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Analog Computer Plus LITERATURE CITED( 1 ) Crout, P. D., Trans. A m . I m t .

In order to achieve the advantages of automatic operation, an automatic quartz tube oomhustion apparatus has been developed for the determination of sulfur and halogens in organic materials. The sample is vaporized in a stream of nitrogen and combustion occurs in the high temperature zone of the combustion tube, where a stream of oxygen is injected. A thermooouple, located just beyond the point at which oxygen is introduced, senses the heat generated by the combustion of the sample vapors and controls the amount of heat that is applied to cause vaporization of the sample. The apparatus reduces the training which must be given the operator, eliminates improper combustions resulting from errors in judging the volatility of samples, and automatically burns each sample at the maximum safe rate. An operator oan complete 15 to 25 analyses per 8-hour day with virtually no possibility of losing an analysis heoause of improper combustion.HE quark tube combustion method ( 1 ) is widely used in the T petroleum industry for determining sulfur and halogens in organic materials. I n this method the sample, contained in a combustion boat, is vaporieed in a stream of air by gradually applying heat to the sample boat. This technique requires the constant attention of the operator, and his experience and training are important factors in achieving properly controlled vaporization of the sample.In attempts to design an apparatus which would allow more rapid combustion and would facilitate the combustion of volatile materials, a unit was constructed in which the sample was vaporized in a stream of nitrogen and the vapors were mixed with oxygen within the heated zone of the combustion tube. The observation that an intense flame resulted in the zone of admixture of oxygen and sample vapors suggested the possibility of Using the flame temperature as a measure of the rate of sample vaporization. In preliminary tests a thermocouple was located in the flame and the temperature indicated by a pyrometer was used to guide the rat0 at which heat was manually applied to vaporize the sample. The direct relationship found between the flame temperature and sample vaporization rate suggested that the former could be used as the basis for automatic control of the latter. As a result of further investigation along these lines, an apparatus was developed which provides completely automatic sample combustion.Combustion is carried out in a horizontally mounted quartz tube, a portion of which is maintained at 1000' C. The sample is placed in the cool zone of the tube and rapidly heated by applic* tion of full line voltage to a bare wire coil on the outside of the tube. Sample vapors are swept into the heated zone by a stream of nitrogen and mixed with a large excess of oxygen, at which point they burn with an intense flame. The rate of sample vaporization is controlled by a thermocouple located in this flame. The thermocouple, by means of an amplifier and relay circuit, switches the heater off and turn8 on a cooling air blast, or switches the heater on ...

The proposed volumetric method for the determination of magnesium in carbonate ores involves removal of most of the calcium as the sulfate, precipitation of magnesium hydroxide with excess standard alkali, and titration of the excess with a standard acid. When methyl red is used as the indicator, 0.50 A7 sodium hydroxide solution that is not carbonate-free can be satisfactorily used. Any indicator having the same pH range as methyl red could be used, but methyl red was selected because it is used in many laboratories as an acid-base indicator.' Common impurities such as iron and aluminum are removed as insoluble hydroxides at the methyl red end point and manganese can be removed by oxidizing it to insoluble manganese dioxide with alkali peroxide.This method gives results that are comparable with those ob-tained with the conventional gravimetric pyrophosphate method. It does not require as much time as the pyrophosphate method and should be useful for the routine analysis of magnesium carbonate ores.