Neutralization method for determination of sulfur

The sample is burned in a stream of air (or carbon dioxide, oxygen) at 1250-1300 °, and the sulfur in the sulfide and sulfate is dissolved in sulfur dioxide. The hydrogen peroxide is absorbed into the sulfuric acid, and the methyl red primary methyl blue mixed solution is used as an indicator, and titrated with a sodium hydroxide standard solution.

First, the reagent

Hydrogen peroxide absorption solution, 1.25%, take hydrogen peroxide (30%) 25 ml, dilute to 600 ml with water, shake. Add 25 ml of 0.2% methyl red solution (60% ethanol solution) and 5-6 ml of 0.2% methylene blue solution (aqueous solution) and shake well.

Sodium hydroxide standard solution, 0.05N, 2.0 g of sodium hydroxide dissolved in boiled and cooled water, diluted to 1000 ml, and stirred. Store in a lower mouth bottle with a soda asbestos tube.

Calibration, accurately weighed 0.2-0.5 g of reference potassium hydrogen phthalate which had been baked at 120 ° for 1-2 hours, placed in a 250 ml Erlenmeyer flask, and dissolved in 100 ml of warm water. Add 2-3 drops of phenolphthalein indicator agent, titrate with 0.05N sodium hydroxide standard solution until the solution is pink.

N=(W×1000)/(204.2×V)

T=N×16.3

Wherein the weight of potassium hydrogen phthalate (g);

V-titration consumes milliliters of sodium hydroxide standard solution;

The equivalent concentration of the N-sodium hydroxide standard solution;

Titration of sulfur to T-sodium hydroxide standard solution (mg/ml).

Or use a standard sample to calibrate the titer of sulfur in the sodium hydroxide solution.

Second, the analysis procedures

Before the measurement, increase the furnace temperature to 1250 °, pass the air flow, check whether the instrument device leaks, and make a blank test.

A sample of 0.1-0.2 g was weighed and placed in a porcelain boat fired at a high temperature, and 0.2 g of copper oxide was added as a flux.

Weigh 100 ml of hydrogen peroxide absorption solution and place it in the absorption bottle. The porcelain boat containing the sample was pushed into a porcelain tube which had been heated to 1250°, preheated for 30 seconds, and air flow was introduced to make 2-3 bubbles per second. After burning at 1250 ° for 5-10 minutes, the absorption liquid is red, and titrated with a sodium hydroxide standard solution until the solution becomes stable bright green.

%S={[V×(T/1000)]/G}×100

Where the V-titration consumes the milliliters of the sodium hydroxide standard solution;

Titration of sulfur to T-sodium hydroxide standard solution (mg/ml);

G-sample weight (grams).

Paper Bag Adhesive

Kraft paper bags are favored by everyone because of their environmental protection characteristics, especially in almost all European countries using kraft paper bags, so there are several ways of kraft paper bags.
1. Small white kraft paper bags. Generally, this kind of bag is large in quantity and widely used. Because many businesses require this kind of kraft paper bag to be cheap and durable, usually the method of this kind of kraft paper bag is machine-shaped and machine-sticked. machine operated.
2. The practice of medium-sized kraft paper bags. Usually, medium-sized kraft paper bags are made of kraft paper bags that are machined and synthesized and then manually pasted with ropes. Because domestic kraft paper bag forming equipment is limited by the molding size, and kraft paper bags The rope sticking machine can only stick the rope of the smaller tote bag, so the practice of the kraft paper bag is limited by the machine. Many bags cannot be produced by the machine alone.
3. Large bags, reverse kraft paper bags, thicker yellow kraft paper bags, these kraft paper bags should be made by hand. There is no machine in China that can solve these kraft paper bags, so they can only be made by hand. The production cost of kraft paper bags is high, and the quantity is not large.

4. No matter what kind of kraft paper bag above, if the quantity is not large enough, it is generally made by hand, because the loss of machine-made kraft paper bag is large, and there is no way to solve the practice of small quantity of kraft paper bag.