43 results about "Starch indicator" patented technology

The invention discloses a rapid quantitative detection method for determining iodine content in well salt. The method comprises the following steps: (1), an appropriate amount of iodized salt is weighted, placed in a bottle and dissolved in water; (2), an appropriate amount of phosphoric acid is added in the bottle first to provide an acidic condition, then an appropriate amount of sodium hypochlorite solution is added and mixed evenly to oxidize iodine ions into iodate ions, and then an appropriate amount of oxalic acid solution is added to remove the residual sodium hypochlorite after the reaction with iodide irons; (3), an appropriate amount of potassium iodide solution is added in the bottle to allow full reaction between potassium iodide and iodate ions; (4), the solution in the bottle is titrated with sodium thiosulfate solution until the color of the solution in the bottle turns to be faint yellow; (5), starch indicator solution is added in to the bottle and shook evenly and then the solution in the bottle is titrated with the sodium thiosulfate solution until the color of the solution in the bottle disappear; and (6), the iodine content of the iodized salt is worked out according to the consumption amount of the sodium thiosulfate solution. Therefore, the method provided by the invention can be used to quickly and accurately determine the total iodine content in the well and rock salt.

The invention discloses a revertose detection method, comprising the following steps: sequentially adding 10-15ml of liquid A, 10-15ml of liquid B and 0.5-1.5ml of a sample solution (glucose equivalent is 30-80mg) to a triangular flask of 250ml; supplementing the triangular flask with distilled water until the total volume of the liquid in the triangular flask is 50ml; heating and boiling for 2-5 minutes, and quickly cooling to room temperature; adding 5-15ml of liquid C and 5-15ml of liquid D, and titrating liquid E, when the end point is approached, namely the color is faint yellow, adding 2-3ml of 12% starch indicator, and when the tested solution becomes purple, continuing to titrate, so that the tested solution becomes pink from purple, thereby reaching the end point. The revertose detection method has the beneficial effects that thermal titration is not needed, and the method is simple and safe to operate, low in consumption of glucose standard solution, fast in operation and accurate in data.

The invention relates to a method for detecting methylene blue absorption quantity of montmorillonite. The method comprises the following steps: (1) dispersing a montmorillonite test sample into water, adding a sodium pyrophosphate solution, stirring uniformly, heating to slight boiling and cooling to room temperature; (2) adding an excessive methylene blue standard solution, stirring to perform complete reaction, generating precipitate, filtering, collecting filtrate, adding a potassium dichromate standard solution into the filtrate, performing water bath, cooling and filtering, washing withwater and collecting the filtrate; (3) adding a sulfuric acid solution and potassium iodide and shaking up; and (4) performing titration by using a sodium thiosulfate standard solution until the solution is faint yellow, adding several drops of starch indicator olution is faint yellow to enable the solution to be blue, and performing titration until blue color disappears, wherein bright green color is the end point. Compared with the prior art, the method has the following advantages: the used reagents are wide in source and moderate in price; and the result obtained through measurement by the measuring method is high in repeatability and is accurate and effective.

The invention is a testing method of recovered glycol purity, weighing 0.6-0.8g of glycol sample and placing it into 250 ml volumetric flask and diluting with water to scale and shaking uniformly; using pipette to absorb 5 ml of solution obtained and adding in 250 ml iodine measuring flask and absorbing 20 ml of high-iodine solution and adding in the iodine measuring flask and shaking uniformly; placing for 30 min in 45 deg.C constant temperature water bath and taking out and cooling to room temperature; adding in 10 ml of 20% KI solution and 100 ml of water, and placing in dark place for 10 min and titrating with 0.1 mol/L Na2S2O3 to buff; adding in 1 ml of 1% starch indicator and continuing titrating until blue disappears, able to directly reflect concrete value of glycol purity and accurately find measuring proportion to new glycol without special instrument, and the invention has characters of simple and convenient, rapid, highly accurate and good precision.

The invention provides a method for detecting sulfur content in sulfur paste. First, the sulfur paste to be detected is sampled, then the sample is dried, and then the sample is weighed. Then, the sample is put into a flask, and then distilled water is added to the flask, and then Then add excess sodium sulfite, then heat and distill until all the samples in the flask are dissolved, then add formaldehyde, acetic acid and starch indicator to the sample solution, then titrate with iodine standard solution, and then calculate sulfur according to the consumed volume of iodine standard solution The sulfur content in the paste; the detection method can not only effectively avoid the use and generation of toxic drugs, but also greatly improve the work efficiency; and the principle is simple, the operation is convenient, and the operation cost is low, so it is worthy of popularization and promotion.

The invention discloses a detection method of tin content in high concentration tin hydroxide. The method comprises the following steps: step 1, dissolving test sample completely in concentrated hydrochloric acid to form the tin tetrachloride solution to be tested, step 2, synchronously stirring and adding diluted hydrochloric acid solution with 4-6 times of volume of the test solution into the solution to be tested to obtain the mixed solution, step 3, adding zinc powder in the mixed solution for a plurality of times for reduction reaction, step 4, adding starch indicator in the clear and transparent solution prepared in step 3, using potassium iodate standard solution to conduct the titration, based on the titration results calculating the tin content in the tin hydroxide. The mass content of the tin element in the test sample is no lower than 30%. According to the detection method, the principle of reduction titration method is applied, accompanied by the control of the reducing agents and the infusion manners of the reducing agents, to achieve the complete reduction of the tin with four covalent bonds in the sample with a high tin content. Repeated tests confirm a good reproducibility of the test results.

The invention discloses a reaction endpoint judgment device. The device comprises a reaction container, a burette arranged above the reaction container, a monochromatic light source arranged on one side of the outside of the reaction container and a photoelectric receiver located on the other side of the reaction container and opposite to the monochromatic light source, wherein the photoelectric receiver is connected with a data processing system. The invention further discloses five-step iodometry without the step of starch adding. The device and the method effectively solve the problems that color change of a reaction endpoint is influenced and errors are caused to judgment of the titration endpoint due to the fact that a starch indictor is likely to have a reaction with high-concentration iodine in advance in step 2 and step 4 in traditional five-step iodometry and starch forms colloid and wraps the iodine, the device is simple in structure, the method is simple and convenient to operate, and the sensitivity and the accuracy are high.

The invention relates to a method for detecting a content of vitamin C in a vitamin C solid beverage in the field of analysis. The detection method comprises the following steps: collecting a sample solution to be detected, and determining by virtue of an iodometric titration method; adding a starch indicator, and recording the consumed volume of an iodometric titration solution; calculating a content of the vitamin C; wherein the sample solution to be detected is formed by mixing a solid sample, water and an acetic acid dilute solution. The raw material reagent is easy to get, the application of instruments is wide, the operation is simple, a detection result is accurate, and the detection cost is low.

The invention provides a detection method for content of iodine in amino acid iodized salt. The method comprises the following steps of dissolving a to-be-detected sample in water, adding potassium ferrocyanide and zinc acetate, and filtering; (2) adding a mixed solution of oxalic acid and phosphoric acid into filtrate, adding a sodium hypochlorite solution, and heating the mixed solution until boiling; (3) rapidly cooling the boiled mixed solution to below 30 DEG C, adding a potassium iodide solution, titrating with a sodium thiosulfate standard titration solution to be pale yellow, and adding a starch indicator; and (4) continuously titrating with a sodium thiosulfate standard titration solution until blue just disappears as the end point. The detection method disclosed by the inventionsolves a problem that the content, which is detected by a national standard method, of the iodine in the amino acid iodized salt is low, the detection method is accurate and reliable, no extra detection instrument is needed, the operation is easy, and the method is easy to popularize and apply.

The invention discloses a method for determining contents of 1,2-diol connection structures in polyvinyl alcohol. The method is characterized in that after a to-be-tested polyvinyl alcohol sample is dissolved in water; periodic acid is added for complete reaction; potassium iodide is added for placing in dark place for 5-15 min; and finally sodium thiosulfate solution is adopted to carry out quantitative titration under the display of a starch indicator until the solution is colorless, and a volume of consumed sodium thiosulfate solution is recorded so as to calculate a content of a 1,2-diol connection structure in the to-be-tested polyvinyl alcohol. The method for determining the contents of the 1,2-diol connection structures in polyvinyl alcohol is simple to operate and stable and correct in data, and has an important application value.

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 provides a method for measuring the residual sulfur dioxide content of tortoise jelly powder. The method has the advantages of short operation time and small detection error. The method comprises the following steps: (1) processing a sample; (2) distillation: adding 8 mL of hydrochloric acid into a distillation tube, immediately installing the distillation tube on a Kjeldahl apparatus, rotating the distillation tube to completely seal the distillation tube, opening the distillation switch, carrying out distillation under heating for 6 to 10 minutes, inserting the lower end of a condensing tube into an iodine flask containing 20 mL of iodine absorption liquid, closing the distillation switch to stop distillation when the volume of distillate in the iodine flask reaches 120 mL, and washing the pipe that is inserted into a lead acetate absorption liquid with a little amount of water, and carrying out a blank experiment at the same time; (3) dropwise adding 8 mL of concentrated hydrochloric acid and 1 mL of starch indicator into the iodine flask in sequence, shaking, dropwise adding an iodine standard titration solution until the solution becomes blue and blue color lasts for at least 30 seconds, and recording the volume of used iodine standard solution; (4) calculating. The invention belongs to the technical field of chemical detection.

The invention relates to a quantitative determination method for carbon-carbon double bonds on the surface of powder, which comprises the steps of weighing Wg of powder, adding into an iodine flask, adding an organic dispersant, and stirring; adding an excessive iodine bromide solution into the iodine flask, stirring, placing in a dark place, adding distilled water and a potassium iodide solution, and uniformly shaking; using a sodium thiosulfate solution with the molar concentration of c mol/L for titration, shaking the iodine flask till the solution becomes light yellow, adding a starch indicator, continuing the titrationtill blue disappears, repeating the experimental group for multiple times, and taking the average volume of the sodium thiosulfate solution consumed each time to be V1 mL; and taking the volume of the sodium thiosulfate solution consumed by the blank control group to be V2mL. The calculation formula of the content X% of the carbon-carbon double bonds is shown in the description. The quantitative determination method for the carbon-carbon double bonds on the surface of the powder is low in cost, high in accuracy, simple and convenient to operate, good in repeatability and suitable for determination of the content of the carbon-carbon double bonds in the polyalkyl silsesquioxane micro powder.

The invention relates to a method for measuring the iodine content in feedstuff. The method includes the following steps that 1) a calcium iodate sample,a sulfuric acid solution and water are mixed tobe heated,then filtration is carried out while heating,washing is carried out,filter liquid and washing liquid are collected and mixed,and to-be-measured liquid is obtained; 2) a ferrous sulfate solution and a starch indicator solution are added into the to-be-measured liquid,then a sodium thiosulfate standard solution is titrated till the to-be-measured liquid is colorless,and the iodine contentis obtained after calculation. Compared with the prior art,the method can be used for rapidly and accurately measuring the iodine content in 1%-10% calcium iodate of the feedstuff,reference data is provided for purchasing and acceptance inspection of the feedstuff,and meanwhile the method is of great significance in feed quality safety; reagents used in the measuring method is wide in source andmoderate in cost,and a measured result is good in repeatability and accurate and effective.

The invention is applicable to the technical field of agricultural product detection, and provides a method for determinating the content of sodium metabisulfite in ginger. The method comprises the following steps: cleaning impurities and soil on the surfaces of gingers, and then uniformly cutting to obtain ginger blocks; drying the ginger blocks, then performing vacuum drying, and then crushing to obtain ginger powder; weighing the ginger powder, putting into an iodine volumetric flask, then accurately transferring an iodine standard solution to the iodine volumetric flask, dissolving by uniformly shaking, then adding an acid solution into the iodine volumetric flask, titrating with a standard solution of sodium thiosulfate after completion of addition, then adding a starch indicator nearthe end of titration, and continuing titration till the end of the titration. By the method, an end point is easy to judge and the detection limit is relatively low, and the method is suitable for detection of a low-content sample; and meanwhile, the determination accuracy and the determination precision are relatively high.

The invention provides a detecting method for 2, 5-dyhydroxy-1, 4-dithiane content. A 2, 5-dyhydroxy-1, 4-dithiane sample is added in an iodine flask, 100 milliliters of purified water and 10 milliliters of sulfuric acid solution are added, dissolution is performed for 20-30 minutes, 50 milliliters of iodine solution is added after complete dissolution of the purified water and sulfuric acid solution and mixed uniformly, titration is carried out with 0.1040 N of sodium thiosulfate standard solution until the color is pale yellow, 1 milliliter of starch indicator is added, and the titration iscontinuously carried out until the color is colourless and white to the end. Compared with a traditional gas chromatography detecting method that a 2, 5-dyhydroxy-1, 4-dithiane primary standard substance is taken as a contrast for comparison, the detecting method does not need gas chromatography, the primary standard substance is not needed, the method has the advantages that the equipment investment is less, the detecting is simple and convenient, the data is parallel and stable, the detecting cost is low, and the operation is easy, and the detecting method is applicable to production detection.

The invention relates to a low-detection-limit detection method for ClO2 <-> in water, which uses a photo-thermal potential analyzer and comprises the following steps: S100, preparing a ClO2 <-> solution by using distilled water, adding a phosphate buffer solution into the ClO2 <-> solution, and adjusting the pH value to 6-8; S200, adding potassium iodide into the solution obtained in the step S100, and dissolving to obtain a solution to be reacted; S300, adjusting the pH value of the to-be-reacted solution to 2-3 to obtain a reaction solution, and immediately putting the reaction solution in a dark place to react for 5-6 minutes; S400, adjusting the pH value of the solution obtained in the step S300 to 3-5, simultaneously adding a starch indicator and potassium iodide, mixing and dissolving, and immediately titrating by using a sodium thiosulfate standard solution when the photometric electrode starts to feed back a signal; and S500, recording the volume of the consumed sodium thiosulfate standard solution at the titration end point, and calculating the concentration of ClO2 <-> in water.

The invention relates to a detection method. Particularly, the invention relates to a method for testing the content of residual dimethyl sulfoxide in polyacrylonitrile precursor in a carbon fiber production process. The method comprises the steps: measuring a sample to be measured into a round-bottom flask; adding a certain amount of deionized water for mixing; after the solution is cooled, preparing a 1000mL aqueous solution, adding a certain amount of potassium permanganate solution, adding dilute sulfuric acid, uniformly shaking, measuring an aqueous solution prepared from a to-be-detectedsample, adding a potassium iodide solution, uniformly shaking, titrating with a sodium thiosulfate solution until the solution is light yellow, adding a starch indicator, and continuously dropwise adding until the solution is colorless. The testing method disclosed by the invention is a testing method capable of simply and accurately testing the content of the residual dimethyl sulfoxide in the polyacrylonitrile precursor, and the problem that the content of the residual dimethyl sulfoxide in the polyacrylonitrile precursor cannot be accurately tested at present is solved, so that the contentof the residual dimethyl sulfoxide in the precursor is accurately controlled.