RU2056629C1 - Method of phase analysis of composition of mineral formations - Google Patents

Abstract

FIELD: analytical chemistry. SUBSTANCE: automation of method gives rise to increased sensitivity, authenticity and productivity of phase analysis by way of sample exposure of spectrum in equal prest time intervals during process of coming of sample into arc discharge. Registration of fact of change of intensity of spectral lines under condition of fraction distillation amounts to phase analysis. EFFECT: increased sensitivity, authentisity and productivity of analysis. 2 cl, 2 dwg

Description

 The invention relates to analytical chemistry of rocks, minerals, loose deposits of other multicomponent formations and can be used in geochemistry to study the mobility of ore and dispersed elements in rocks and rock-forming minerals, in ecology to highlight the anthropogenic part of introduced elements from their natural content in natural formations, for studying isomorphism, studying the process of enrichment of rare-metal, polymetallic and other ores, for analytical control of standard samples of personal level, and others.

 As an analogue, A.K. Rusanov’s solution can be used when studying the sequence of fractional receipt of chemical element compounds in an arc discharge from the formed ore and mineral melts in the electrode channel [1] The data obtained made it possible to compose the volatility series of elements, sulfide and other compounds during the evaporation of mineral substances from the channel of the carbon electrode. They contribute to the rational choice of the conditions for the excitation of the spectrum, the selection of buffer compounds added to the sample in quantitative analysis in order to increase the detection sensitivity of specific elements and increase the accuracy of determining their content in the analyzed samples.

 The arrival of chemical elements into the plasma of an arc discharge from melts in the electrode channel was recorded on a uniformly moving photographic plate when designing the light flux on the spectrograph's entrance slit.In the spectrograph design, a device for moving a cartridge with a photographic plate along the guides from the rotation of the screw is provided. In the spectra, the change in the blackening of the lines of the elements of the main components of mineral formations and composed mixtures of elements was visually evaluated. In this case, only those lines were considered in which there was no self-reversal effect. The sequence of the entry of elements into the discharge plasma was determined from the mutual displacement in the spectrogram of the lines.

 The device with continuous movement of the cartridge (photographic plate) does not provide a clear image of the contour of the lines and their exact fixation in time.

 A prototype can be a method for separating chemical elements in fractional distillation mode to detect differences or correspondences of the element entry form in the analyzed samples and in the standard samples used [2] As an example, the phase separation of cadmium for sphalerite and synthetic standards is shown by fixing the spectrum onto a moving photographic plate through some time intervals during the arc discharge of the evaporation (emission) of the sample from the channel of the electrode. From sphalerite (a natural mineral), zinc and cadmium from the electrode channel evaporate synchronously during the entire emission time. From a synthetic mixture of compounds (preparations) of cadmium and zinc, the duration of evaporation of zinc and cadmium are sharply different. Cadmium evaporates in the initial stages of the arc discharge, which leads to a significant discrepancy in the intensity of the spectral lines of these elements in natural and synthetic standards.

 Sequential photographing of a number of spectra during the evaporation of a sample of a sample from the electrode channel provides the movement of the spectral instrument cassette. Spectrographs, as a rule, have devices for moving the cartridge (in a vertical plane) along the guides with the help of a lead screw and a nut fastened to the cartridge. A diaphragm (curtain) installed in front of the spectrograph entrance slit limits the height of the instrument entrance slit. To accurately combine the spectrum of iron (as a wavelength scale) and the spectrum of the sample, a curtain is used with holes (windows) at different heights (butt-shot spectra). The shutter can be used to photograph the spectrum in two exposures under various excitation modes.

 The disadvantages of the method. Sensitivity loss is inevitable, since when moving a plate by moving a plate, the light flux of the discharge during its movement (to the next stage) is blocked, the exact arrangement of the spectra one below the other is not ensured. Moreover, it is difficult or impossible to maintain uniform fixation of the entire series of spectra at short intervals. A clear phase separation of chemical elements is possible only with a significant content in the sample.

 For geochemical studies, the study of the mobile form of ore, other chemical elements in rocks, in other natural formations is of national economic importance (prospecting, forecasting deposits). Of practical interest here are the average (clarke) contents of chemical elements in rocks ten thousandths, thousandths, hundredths, tenths of a percent.

 Phase analysis is also necessary in ecology to establish the degree of mobility of elements that represent a potential hazard. And here the concentration of scattered elements is a small fraction of a percent.

 The technical result of the invention is the automation of the method, which entails an increase in the sensitivity, reliability and productivity of phase analysis by accurate reproduction of the expanded spectrum in time by fractional exposure at equal given intervals during fractional distillation of the transient receipt of the sample in an arc discharge.

 According to the proposed method for phase separation of chemical elements, the spectrum of the sample is photographed stepwise at predetermined equal time intervals in the process of its entry from the melt in the channel of the carbon electrode into the arc discharge plasma. Exactly maintain the specified exposure time of each stage of the overall (expanded) spectrum. The entire series of spectra is fixed exactly one below the other on a fixed photographic plate by means of stepwise illumination by arc discharge of various sections of the spectrograph's entrance slit during its automatic movement. The mode of moving the curtain with a window located at an angle to the slit of the device eliminates a break in the illumination of the entrance slit of the spectrograph from an arc discharge, which contributes to obtaining a high detection sensitivity of the element.

 A series of spectra is obtained at equal predetermined time intervals during fractional distillation of the transient receipt of the sample from the channel of the electrode into the arc discharge. From the unfolded general spectrum of the sample, the change in the intensity of the spectral lines of chemical elements from spectrum to spectrum is recorded and the nature of the change in the intensity of the lines in the series of spectra is used to conclude that the phase composition of the sample determines the occurrence form of elements of elements constituting mechanical impurities (mobile form) and elements isomorphically connected with the crystal lattice of the sample.

 The advantage of the proposed method is the registration of a transient process (measured in seconds) in short equal time intervals without loss of light flux of the arc discharge, which ensures high sensitivity during phase separation of elements (from ten thousandths, thousandths of a percent or more), suitable for solving geochemical and environmental problems. The spectrum is fixed on a fixed photographic plate by instantly moving the light by the discharge light flux (diaphragm) of various sections of the plate, therefore, when switching from spectrum to spectrum, there is no loss of emitted light from the source of excitation of the sample spectrum. The luminous flux is fully used during each interval to fix the component spectra when scanning the full spectrum of the sample. The time-resolved spectrum is obtained as a series of individual spectra at precisely specified time intervals by automatically turning on the ignition of the discharge through a time relay.

 The speed and accuracy of automatic registration of the expanded spectrum over time (increasing the productivity and quality of phase analysis) is also an advantage of the proposed method. At the same time, the spectra in the compared series on the plate are located end-to-end (exactly under each other without displacement), which makes their comparison more convenient and reliable.

 The method is implemented using the device, the purpose of which is the sequential acquisition of spectra through predetermined equal time intervals to fix the transient process of fractional distillation of the sample during the time of excitation of the emission spectrum.

 Figure 1 shows a schematic diagram of a drive (device) for moving the shutter (diaphragm) 3 in front of the entrance slit 6 of the spectrograph 4 by eight or twelve positions of the shutter 3 to obtain a sequential series of spectra without moving the photographic plate (spectrograph cassette). The upper end of the lever (rod) 7 has a hinge mount on the bracket, which is mounted on the housing of the spectrograph 4 (not shown). The lever 7 can swing relative to the hinge in a vertical plane parallel to the plane of the entrance slit 6. The lower end of the lever 7 is connected to the movable rack 9 in the same plane. The movement of the lower end of the lever 7 from the rack 9 through the stop 8 transfers the movement to the shutter 3. The distance from the axis of rotation of the lever 7 (upper end) to the stop 8 is approximately ten times less than the distance from the stop 8 to the lower end of the lever 7. This ensures small accuracy movement of the curtain 3. Moving the cutout (window) 5 of the curtain 3, located at an angle to the slit of the spectrograph, opens the subsequent sections of the slit 6 to obtain the next spectrum, since the window 5, located directly in front of the entrance (vertical) slit 6 of the spectrograph 4, is its perpendi ulyarnym movement relative to the slit 6, the radiation passes through the discharge arc 1 various portions of the slit 6 that provides a predetermined series of spectra in the process proceeds sample vapor in an arc discharge. To rotate the gears of the drive 10 use a serial motor type RD-9 with a gearbox. Scales 11 control the operation of the device.

 Half the rotation of the drive shaft 10 through a gear wheel moves the rack 9 to one eighth of its full movement (one step). The rotation of the drive shaft 10 by one third determines, respectively, twelve fixed positions of the curtain 3 in front of the slit 6 of the spectrograph 4.

 In the power supply circuit of the motor (figure 2) included a standard time relay BRV. The relay allows you to accurately maintain a given exposure (in time) upon receipt of each fixed spectrum. After exposure of the first spectrum, the BRV turns on the motor M to move the curtain one interval, the second spectrum is fixed, similarly all subsequent ones.

 By switching the direction of rotation of the motor shaft (toggle switch 1), the cremallier is returned to its original position. End microswitches restrict the movement of the rack in the initial and final position (not specified). The free contacts of the microswitches are used to power up the signal devices.

 To automatically turn on the exposure and then transfer the shutter (aperture) when recording the entire series of spectra, the following changes were made to the inclusion of the time relay unit (BRV). The KN start button is shorted through the closed side contacts 12 of the additional magnetic starter P (in the off position). The magnetic starter P is included in the BRV circuit through the contacts of the gate connection (socket "gate"). When the magnetic starter P is triggered (after exposure of the first spectrum) through its side contacts 13, motor M is switched on for 1-2 s. When the cam disk is rotated on the motor shaft, the pin of the microswitch 14 drops out of the recess and the electric motor is powered through its closed contacts. With further rotation of the disk, the pin of the microswitch 14 sinks into the subsequent recess and the rotation of the motor shaft M stops. At the moment of operation of the magnetic starter, contact 12 breaks the circuit of the KN start button circuit (when the ON position is on), "freeing" it for the next exposure on (this is a condition of the BRV circuit). At the same time, on the remote control panel the arrow of the "exposure" scale should be set to the division corresponding to 1-2 s. When the ON switch is closed, the cycle repeats. Thus, at any given exposure (on the BRV scale “firing”), the proposed device automatically reproduces in time the expanded spectrum on a fixed plate by fractional exposure during fractional distillation of an arc discharge plasma, which eliminates the loss of emission from the spectrum to the spectrum and together with high accuracy of exposure of each spectrum determines the reliability and increases the sensitivity of the phase analysis of the composition of the analyzed sample, the essence of which lies in recording changes in the intensity of the spectral lines of the chemical elements of the sample in the fractional distillation mode. Naturally, the automatic translation of the spectrograph slit shutter and the simultaneous inclusion of the desired exposure increase labor productivity.

) показывает, что свинец в образце содержится в виде самостоятельного минерала как механическая примесь (установлено минералогическим анализом), фиксируется в начальной стадии фракционной дистилляции. Другой элемент титан частично входит в кристаллическую решетку составляющих минералов, фиксируется синхронно с основными компонентами пробы (алюминий, магний, кремний, железо). Кроме того, титан фиксируется как примесь в конечные стадии дистилляции, подтверждено минералогическим анализом присутствие титана в пробе в качестве самостоятельных минералов. Хром, содержащийся в пробе, фиксируется синхронно с линиями железа, магния, кремния, изоморфно входит в кристаллическую решетку основных минералов образца.The scan of the total spectrum of a sample of low-iron bauxite with a high content of lead and titanium (spectrograph STE-1, wavelength of lines in

) shows that the lead in the sample is contained as an independent mineral as a mechanical impurity (established by mineralogical analysis), is fixed in the initial stage of fractional distillation. Another element, titanium, partially enters the crystal lattice of the constituent minerals and is fixed synchronously with the main components of the sample (aluminum, magnesium, silicon, iron). In addition, titanium is fixed as an impurity in the final stages of distillation; the presence of titanium in the sample as independent minerals is confirmed by mineralogical analysis. The chromium contained in the sample is fixed synchronously with the lines of iron, magnesium, silicon, and isomorphically enters the crystal lattice of the main minerals of the sample.

 Lead, in contrast to the first example, although at a significantly lower concentration, is fixed in the granite sample synchronously with the main components of the sample (magnesium), which indicates its isomorphic relationship with the crystal lattice of the main components of the sample.

 The advantage of automating phase analysis, which is manifested in an increase in its sensitivity and productivity, is very significant on the example of geochemical searches when studying the mobility of ore and dispersed elements in rocks and rock-forming minerals, since the task of geochemistry is not only in determining the qualitative and quantitative composition of elements, but also in establishing the forms of their location, it is the form of location that determines the migratory capacity of the elements, which characterizes the ore content of certain areas. Thus, for any geochemical study, it is important to know that in the studied object there is not only a lot of this or that element, but also that a significant part of it is “migratory capable”. It is these issues that can be solved by highly sensitive and productive phase analysis.

Claims (2)

 1. The method of phase analysis of the composition of mineral formations, including the evaporation of the sample and the excitation of its emission spectrum by means of an arc discharge, registration in the process of fractional distillation of the spectra of the sample when illuminated by the discharge of the entrance slit of a spectrograph equipped with a shutter placed in front of the slit, establishing the forms of the presence of chemical elements in the sample, characterized in that a series of spectra located strictly one below the other are recorded on a stationary photographic plate by stepwise illumination with a discharge p different sections of the entrance slit of the spectrograph due to automatic movement of the shutter, while the regime of moving the shutter is chosen so as to exclude interruptions in the illumination of the slit, the change in the intensity of the spectral lines of chemical elements from the spectrum to the spectrum is recorded, and the shape of the chemical elements in the sample.  2. A device for phase analysis of the composition of mineral formations, including an arc discharge excitation source and a spectrograph equipped with an entrance slit and a shutter, the discharge gap being optically connected to the spectrograph entrance slit and the shutter placed in front of the slit, characterized in that the device further comprises a drive, equipped with an electric motor, a magnetic starter and a time relay, moreover, a window is made in the curtain, located at an angle to the spectrograph slit, the drive is connected to the curtain, and the time relay is magnetically The first starter is connected to the electric motor.

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