ZINC SULPHATE MONOHYDRATE

Zinc sulphate is a widely used chemical and has been known under the name of “White Vitriol”. Although Zinc Sulphate (mono hydrate) occurs in nature in small quantities as mineral Glosarite, this compound is normally manufactured synthetically. It is the colourless white free flowing powder. It exists in powder form of hydrates as, ZnSo4.H2O. Zinc sulphate is also found in three hydrates forms whose molecular formulas are ZnSo4.4H2O,ZnSo4.H2O. The unstable hydrates are more soluble than stable form. The solubility of the unstable hydrate is 58.7 gm in 10gm of water at 18oc while stable shows only 52.7 gm in 100 grams. The important & popular commercial form of the compound is ZnSo4.7H2O Heptahydrated (21%), & ZnSO4. H2O. In 1978 Mr. P.N. Thakar and Mr. N.S. Randhewa of Punjab Agriculture University Ludhiana worked on “Micronutrients in Indian Agiculture” and established the areas of Zinc deficiency based on sail test and crop responses. In reference to Bihar state they found that zinc deficiency varies from 25% to 75% and even more of the normal value. It was also shown that the response of zinc sulphate was good for rice potato tea in particular and for all the cereals as a whole. The process used for the manufacture of zinc sulphate on commercial scale is simple but technical grade salt can be produced by treating zinc ash or zinc dross (a waste by product form galvanizing units) with sulphuric acid and then filtering the slurry followed by concentration of the dilute zinc sulphate solution and finally during the crystals of ZnSo4.7H2O are separated form mother liquor in a high speed centrifuge crystallizer. The product is then dehydrated to ZnSo4.H2O. For analytical reagent grade Zinc sulphate the salt is preferably produced from using zinc metal as the starting raw material because it is having the wide range of applications as fertilizers, rayon pulp, paper, paint & varnish, textile processing pigments, calico printing etc. It is having the high demand in the market, It is the third most important compound of zinc in comparison of zinc oxide and zinc dust. Zinc sulphate is available in technical, pharmaceutical & Chemically pure grades. It is sold as solid, as ZnSo4.H2O or Znso4.7H2O and also as a solution of zinc sulphate. Zinc sulphate is the most widely used zinc salt of any inorganic acid. Its major use is probably in viscose rayon fibre manufacture. As the viscose filament are ejected from the spinners they enter a complex precipitating bath to promote cremulation. It is also used in textile dyeing & printing. The second largest use is in agriculture and animal nutrition. To correct zinc deficiency in soils it is applied to the soil alone or in fertilizers or incorporated pesticides sprays. In animal nutrition it is used as a trace element in feeds. Pure zinc sulphate solution is required for many purpose particularly for the preparation of lithophone zinc sulphide, phosphorous and for the extraction of zinc by electrolytic refining. In a replicated experiment on wheat-groundnut experiment on wheat groundnut rotation in a sandy loam soil of punjab agricultural University. Ludhiana zinc was applied in the form of zinc sulphate at the rate of 0, 2.8 5,6 and 11.2 kg/ha directly to wheat and the residual effect was studied on groundnut. From these results it may be observed that in the first and second years the response to 2.8 kg zinc was 3.2 and 2.2 g/ha and it also increased further with higher rate of zinc application. In subsequent years. However, the differences became smaller through still the effect of zinc was noticeable. In 49 field trials conducted in Andhra Pradesh on cultivators, fields, it was observed that 50 kg. Znso4, on an average, gave a yield increase of 1.9 to 6.2 g/ha.