Other names: White alum, zinc alum

Molecular formula and molecular weight ZnSO4.H2O, ZnSO4.7H2O, 179.47, 287.56

Physical and chemical properties: colorless or white crystals, granules or powder. Odorless and astringent. Weathering in dry air, it loses all crystal water at 280 degrees Celsius and decomposes above 500 degrees Celsius. 1 gram is dissolved in 0.6 ml water and 2.5 ml glycerin. Insoluble in ethanol. The aqueous solution is acidic to litmus. PH value is about 4.5. Containing 1 molecule of crystal water is less likely to agglomerate. The relative density is 1.97. Melting point is 100 degrees Celsius.

Agrochemical properties: one of the indispensable micronutrient elements for plant growth in Zinc City. Zinc is closely related to plant auxin, nitrogen metabolism, organic acid metabolism and enzyme reaction, and it has a great physiological role in plant life activities. Zinc fertilizer has the effects of promoting early crop development and maturity, enhancing crop resistance and increasing grain weight. In agricultural production, the application of zinc fertilizer can greatly increase the yield.

Easy identification

1. Color and shape, zinc sulfate heptahydrate is a colorless orthorhombic crystal, and agricultural zinc sulfate is light yellow due to the trace amount of iron. Zinc sulfate heptahydrate partially loses water in the air and becomes zinc sulfate monohydrate. Zinc sulfate monohydrate is a white powder (and there are also granules). Both types of zinc sulfate are not easy to absorb water and will not agglomerate for a long time.

2. Odorless, astringent

3. Solubility: This product is very soluble in water, soluble in glycerin, and insoluble in ethanol. The aqueous solution is colorless and tasteless, and the aqueous solution is acidic.

Qualitative identification: Dissolve the sample in distilled water, divide it into 2 samples, and add one portion to the barium nitrate solution treated with nitric acid to test sulfate ions. The second addition of sodium hydroxide solution will produce precipitation and then gradually dissolve (zinc hydroxide is amphiphilic), but it may also be aluminum sulfate. We need to add hydrosulfuric acid (hydrogen sulfide aqueous solution) to generate zinc sulfide, dry it, and place it in the air to generate zinc sulfate, and the quality will increase, so we can use the method of weighing to see if the quality increases.

When farmers buy zinc sulfate, they need to pay attention to the zinc content. Some products are promoted as magnesium-zinc fertilizer, or iron-zinc fertilizer, whose zinc content is only about 20% of real zinc fertilizer. Please pay attention to this.