48 results about "Iodometric method" patented technology

The invention relates to a process for preparing butadiene from n-butenes, which comprises the following steps:

• • A) provision of a feed gas stream a comprising n-butenes;
  • B) introduction of the feed gas stream a comprising n-butenes and an oxygen-comprising gas into at least one dehydrogenation zone and oxidative dehydrogenation of n-butenes to butadiene, giving a product gas stream b comprising butadiene, unreacted n-butenes, water vapor, oxygen, low-boiling hydrocarbons, possibly carbon oxides and possibly inert gases;
  • C) cooling and compression of the product gas stream b in at least one cooling stage and at least one compression stage, with the product gas stream b being brought into contact with a circulated coolant to give at least one condensate stream c1 comprising water and a gas stream c2 comprising butadiene, n-butenes, water vapor, oxygen, low-boiling hydrocarbons, possibly carbon oxides and possibly inert gases;
  • D) separation of incondensable and low-boiling gas constituents comprising oxygen, low-boiling hydrocarbons, possibly carbon oxides and possibly inert gases as gas stream d2 from the gas stream c2 by absorption of the C₄-hydrocarbons comprising butadiene and n-butenes in a circulated absorption medium, giving an absorption medium stream loaded with C₄-hydrocarbons and the gas stream d2, and subsequent desorption of the C₄-hydrocarbons from the loaded absorption medium stream to give a C₄ product gas stream d1;
  • E) separation of the C₄ product stream d1 by extractive distillation using a solvent which is selective for butadiene into a stream e1 comprising butadiene and the selective solvent and a stream e2 comprising n-butenes;
  • F) distillation of the stream e1 comprising butadiene and the selective solvent to give a stream f1 consisting essentially of the selective solvent and a stream f2 comprising butadiene;
  • where samples are taken from the circulated coolant in step C) and/or the circulated absorption medium in step D) and the peroxide content of the samples taken is determined by means of iodometry, differential scanning calorimetry (DSC) or microcalorimetry.

The invention relates to the technical field of water dissolved gas sensor calibration, and aims at providing a high-precision optical dissolved oxygen sensor calibration method and device. The high-precision optical dissolved oxygen sensor calibration method comprises the following steps: sequentially introducing mixed gases with different oxygen contents into a water-gas mixer, so as to supply multiple dissolved oxygen concentration gradients to a water body; recording a signal value of a dissolved oxygen sensor to be calibrated and a temperature value of the water body, and testing a standard dissolved oxygen value of a water sample by using an iodometric method; calculating a calibration coefficient of the dissolved oxygen sensor to be calibrated. As a practical iodometric method measured value obtained after synchronous sampling is taken as the standard value, the reference value precision of the method is greatly improved when being compared with conventional methods that the concentration of dissolved oxygen in water bodies is calculated according to the water dissolution degree of the mixed gas oxygen concentration; as five temperatures are adopted for sensor calibration, the calibration result is relatively wide in temperature application range when being compared with those of the conventional methods.

The invention relates to a method for measuring bromine in brine through filter paper method sample preparation and X-ray fluorescent spectrometry. Appropriate filter paper is selected for sample preparation, a standard curve is drawn with X-ray fluorescent spectrometry, and the content of bromine in brine is measured through comparison of sample tests. By means of the method for measuring bromine in brine through filter paper method sample preparation and X-ray fluorescent spectrometry, main problems of narrow linearity range, large errors, poor accuracy and precision and the like of a conventional bromine analytical test method are solved, and the method is fast, simple and convenient; compared with the conventional method, the analytical test efficiency is improved by 2-3 times, the analysis cost is low, and the material cost is 10% of that consumed in a sodium hypochloriteoxidation and iodometric method; the testing accuracy is high, the precision is good, the method detection limit is low, and the analysis requirement is met; and besides, the method doesn't need chemical reagent treatment, is particularly suitable for measuring a liquid with bromine content larger than 0.95 mg/L, realizes efficient and environment-friendly bromine measurement and is a real green analysis method.

The invention provides a method for detecting copper, iron and calcium in flash converting furnace slag. The method comprises the following steps: (A) dissolving a flash converting furnace slag test sample with acid to obtain a first solution containing copper ions, iron ions and calcium ions, performing reaction on the first solution, sodium sulfide and sodium hydroxide, and filtering to obtain precipitates and filtrate; (B) dissolving the obtained precipitates with acid to obtain a second solution containing bivalent copper ions and iron ions, masking iron with ammonium bifluoride in the second solution, detecting copper by adopting an iodometry method to obtain the copper content, releasing iron in the solution subjected to copper detection with aluminium trichloride, and detecting iron by adopting the iodometry method to obtain the iron content; (C) titrating the filtrate obtained in the step (A) with edetic acid, thus obtaining the calcium content. The procedures of the detection method provided by the invention are simple, one-step sample weighing is realized, and the contents of three key elements, copper, iron and calcium, in the flash converting furnace slag can be quickly, accurately and continuously measured.

The disclosed combined detection method for high-pure SO3 gas with SO2 as impurity comprises: constant-volume sampling at least 60Deg better 60-80Deg to avoid liquidation of SO3, absorbing with alkali solution to obtain total volume percentage concentration of high-pure SO3 gas and SO2; processing the absorbed liquid, using iodometric method to obtain SO2 volume percentage concentration and then the SO3 concentration. This invention brings an error less than 0.1%.

The invention discloses a one-step method for detecting the concentration of chlorine and chlorinated hydrogen in pollution source waste gas, which has the following steps of: connecting in series two absorption bottles respectively filled with 50 ml of alkali absorption solution with concentration of 0.1-0.2 mol/L for sampling; after collecting the samples, mixing sample solutions in the two bottles, and adding the alkali absorption solution with concentration of 0.1-0.2 mol/L until the total sample solution volume reaches 125 ml; moving 25 ml of solution from the total sample solution to an iodine flask for detecting the concentration of chlorine by using iodometry, and then moving 25 ml of solution sample solution for detecting the concentration of total chlorinated hydrogen in the sample solution by using silver nitrate volumetric method; and finally, calculating the actual concentration of chlorinated hydrogen by using a corrector formula. The method can be used for simultaneously analyzing chlorine and chlorinated hydrogen by one share of absorption solution, and eliminate the positive interference of chlorine to chlorinated hydrogen, thereby accurately determining the concentration of chlorine and chlorinated hydrogen in pollution source waste gas.

The present invention relates to a test method for evaluating the reaction proportion of nascent state oxygen during determination of ozone in water with an iodometric method. According to the present invention, a test method is developed, and is used for solve the problems of the reaction between the nascent state oxygen and the iodide ions and the proportion of the nascent state oxygen occurring the reaction during the determination of ozone in water with the iodometric method; the method is characterized in that the whole set of the test method is designed, a test condition is selected, and the presence of the oxygen occurring the reaction in the nascent state oxygen is determined by calculating the test data, wherein the chemical equation O2+4I+4H<+>=2I2+2H2O exists in the iodometric method; and with the method, when the iodometric method is used to determine the ozone concentration in the water, the determined data is accurate, and the iodometric method is perfect.

The invention provides a technique for detecting the content of copper chloride hydroxide. Only copper chloride in the copper chloride hydroxide is capable of dissolving in water, while cupric hydroxide and copper chloride hydroxide are capable of dissolving in acid. The technique comprises the following steps: dissolving copper chloride hydroxide in water and then filtering, and measuring the content of water soluble chloride ion in the filtrate obtained from filtration by the Volhard titration method; dissolving copper chloride hydroxide in nitric acid, and measuring the total content of chloride ion therein by the Volhard titration method; and dissolving copper chloride hydroxide in hydrochloric acid, and measuring the total content of copper therein by the iodometric method. The accurate contents of water soluble copper chloride, copper chloride hydroxide and cupric hydroxide in copper chloride hydroxide can be calculated through the three steps.

The invention relates to a determination method of furfuryl alcohol content in no-bake furan resin for casting, and belongs to the technical field of detection. The determination method of furfuryl alcohol content in no-bake furan resin for casting comprises the following steps of: determining the content of main ingredient furfuryl alcohol in furan resin by adopting back titration of iodometry, wherein the reaction flow mainly comprises the following substeps of: firstly carrying out bromination reaction on samples, bromine, glacial acetic acid and hydrochloric acid; then dropping in potassium iodide for replacement reaction after bromination; and finally dropping in insodium thiosulfate for reaction. Through the determination method provided by the invention, the furfuryl alcohol content in no-bake furan resin for casting can be determined, so that on one hand, the furfuryl alcohol content can be grasped effectively when the no-bake furan resin is in check-out, the quality for using no-bake furan resin is ensured, the cast quality is stabilized, and the cast rejection rate caused by casts is lowered greatly, and on the other hand, the quality of resin can be evaluated through sample test when new suppliers are developed, so that the test cycle is shortened, the hazard and loss of material object test failure are lowered, and meanwhile basis is provided for confirming the price of resin.

The invention discloses a five-step iodometric method. According to the invention, in the third step of a conventional five-step iodometric method, solution pH value is adjusted to be 12 or higher instead of adding high-purity nitrogen, so that chlorine dioxide in a sample to be detected is transformed into a chlorite and chlorate which are not reacted, separation of chlorine dioxide with chlorine gas is realized, it is not necessary to blow chlorine dioxide and chlorine gas away with high-purity nitrogen, and problems that nitrogen blowing time is controlled to be longer than 40min, treatment time is too long, nitrogen is not easily available, is not convenient to carry, and is dangerous are solved; and in the fourth step, solution pH value is adjusted to be 3 to 7.

The invention discloses a method for improving iodometry measurement accuracy of samples containing interfering substances. According to the method, a proper amount of nonionic surfactant is added on the basis of a conventional iodometry, and the problems that certain samples containing the interfering substances become turbid in the titration testing process and even accurate measurement is difficult due to iodine precipitation are successfully solved. By means of the method, a titration reaction is quick and sufficient, a titration end point is clear and transparent, the end point is accurately judged through color changes of iodine even if starch can not normally display colors, and a test result is good in precision and accuracy. Reagents used in the method are all conventional, safe, free of harm, easy to operate and suitable for being popularized in detection organizations and research institutions.

The invention discloses a method for determining sulfur dioxide in amygdalin contained traditional Chinese medicine and slices thereof. An interference value of an iodometric method is eliminated due to the combination of the iodometric method and a silver nitrate titration method and namely that a difference value of the sulfur dioxide content which is determined by a titration method and the sulfur dioxide content which is determined through headspace gas chromatography and flame photometry is reduced to be within 2 milligrams every kilogram from 370 milligrams every kilogram. The method is simple and convenient, rapid and accurate.

The invention discloses an iodometric method for determining oxygen vacancy concentration in barium ferrite-based lead-free piezoelectric ceramics, belonging to the technical field of ceramic composition analysis. The method comprises the following steps: taking a ceramic sample and grinding into a powder, weighing in a round-bottom flask; adding concentrated hydrochloric acid and stirring until the powder is completely dissolved, and marking the obtained solution in brown yellow color; adding a sodium thiosulfate standard solution into a burette, recording the number of the scale; adding potassium iodide into the brown yellow solution and covering with a plug; vacuuming and then introducing nitrogen gas, stirring evenly, and marking the obtained solution in reddish brown color; titratingto be light brown yellow with the sodium thiosulfate standard solution, adding a starch solution, and marking the obtained solution with dark blue; using the sodium thiosulfate standard solution to titrate until the blue color disappears; recording the numbers of the scales after the twice addition of the sodium thiosulfate standard solution, and calculating the total consumption amount of the sodium thiosulfate standard solution; calculating the valence state of Fe ions in the ceramic sample, and then utilizing charge balance to obtain the oxygen vacancy concentration. The iodometric method provided by the invention is simple and convenient in experimental instruments, simple to operate and accurate and reliable in detection results, and can realize the quantitative analysis of the oxygenvacancy concentration.

The invention relates to a method for measuring content of antimony in a methyltin mercaptide composite heat stabilizer through an indirect iodometric method. The method comprises the following steps that firstly, a certain amount of methyltin mercaptide composite heat stabilizer samples are weighed, concentrated sulfuric acid, concentrated nitric acid and perchloric acid are sequentially added, the volume proportion of the concentrated sulfuric acid to the concentrated nitric acid to the perchloric acid is (2-3):1:1, the proportion of the sample mass to the mixed acid volume is 1: (35-55) g/ml, heating and dissolving are carried out, after the mixture is cooled to the room temperature, a (1+9) hydrochloric acid solution is added for constant volume V, and the mixture is shaken evenly to be used; secondly, the volume V0 of the solution prepared in the first step is moved and taken, a proper amount of potassium iodide and starch indicator are added, a sodium thiosulfate standard titration solution with the molar concentration being 1.000 mol/L is used for titration until the solution becomes colorless from blue so that a titration terminal can be achieved, the volume V1 of the consumed sodium thiosulfate standard titration solution is recorded, meanwhile, a blank test is made, volume V2 is recorded, and the antimony content is calculated according to formula 1 shown in the description. By means of the method, testing results are accurate and reliable, expensive special analytical instruments are not needed, the cost is low, and the method is easy to apply and popularize.

The invention belongs to the field of enzyme activity detection, and relates to a method for identifying suckling pig liver and adult pig liver by utilizing catalase activity. The catalase is extracted from the pork liver by using an extraction method, the activity of the catalase in the pork liver is determined by using an iodometric method and a potassium permanganate method, and the detection method for identifying the adult pork liver and the suckling pork liver, which is high in accuracy, simple and convenient to operate and high in repeatability, is provided. Experiments show that under the same condition, the catalase activity of the suckling pig liver is obviously smaller than that of the adult pig liver, so that the catalase content in the pig liver can be used as an index for identifying the adult pig liver and the suckling pig liver; the method can fill the blank of methods and standards for detecting adult pig liver and suckling pig liver in China, provides a method which is high in accuracy, simple and convenient to operate and high in repeatability for detection of medicinal suckling pig liver raw materials, and has very high application value.

The invention provides a method for detecting the content of sodium thiosulfate in the sodium hexamethylene-1,6-bisthiosulfate dehydrate. A chloride ion content of a to-be-detected HTS sample is measured to avoid the influence on a detection result by chloride ions. When the to-be-detected sample is preprocessed, excessive silver nitrate solution and dilute nitric acid are added; and the dilute nitric acid decomposes sodium thiosulfate in the sample and thus the silver nitrate only reacts with the chloride ion in the HTS. After interference component removing, the content of sodium thiosulfatein the sample can be accurately detected by a simple silver method. The method has advantages of simple preprocessing process, simple operation, and low cost; the interference component in the detection process of the iodometric method can be removed fully; the detection result is accurate; and the method is suitable for large-scale popularization and application.

The invention discloses a high performance liquid chromatography method and application of sodium 3-(benzothiazol-2-ylthio)-propanesulfonate. The method comprises the following steps: (a) providing a 3-(benzothiazol-2-ylthio)-propanesulfonate (ZPS) reference substance solution and a test sample solution; (b) analyzing the ZPS content of the test sample solution in step (a) with HPLC-UV according to an external standard method. Detection conditions are as follows: a chromatographic column uses octadecyl silane bonded silica gel as a filler; a mobile phase is formed by an organic phase and a phosphate buffer, the pH of a phosphate buffer is equal to 5.5 plus/minus 0.1, and the volume ratio of the organic phase to the phosphate buffer is (10 to 90) to (80 to 20); the detection wavelength is between 190nm and 330nm. The technical problems of imperfect measurement method of ZPS content, poor selectivity of iodometric method and poor accuracy are alleviated. The method can accurately detect the ZPS content, so that the precision is good, and the accuracy is high.

The invention provides a method for determining the content of tert-butyl peroxide in diesel oil by infrared spectroscopy. The invention overcomes the defects that an iodometric method is time-consuming and wastes solvents; the determination of tert-butyl peroxide by gas chromatography requires harsh temperature conditions to prevent decomposition; and a low temperature causes the diesel to fail to vaporize thereby contaminating an inlet, a column, and a detector, and resulting in poor reproducibility of the tert-butyl peroxide content determination. The method can conveniently accurately determine the content of tert-butyl peroxide in diesel oil.

The invention discloses a method for detecting iron ions in hydrolysate prepared from buffalo horn powder and application of the method in Qingkailing hydrolysate. According to the method disclosed by the invention, a to-be-detectedhydrolysate is pretreated, and an iodinated compound containing acetyl is added, so that the problem that the iron ions contained in the hydrolysate are difficult to accurately detect due to an end point color reversion phenomenon when the iron ions contained in the hydrolysate are detected by using the existing indirect iodometric method is solved, the interference of the background color of the hydrolysate is eliminated, the end point change is quickly judged through visual and clear color fading, the accuracy and stability of the detection result are guaranteed, real-time detection in industrial production can be realized, the production efficiency is greatly improved, and the product quality is guaranteed.