Цинк сульфид

Химические свойства

Yellowish-white powder. ZnS exists in two crystalline forms, α (wurtzite) and β (sphalerite). Stable if kept dry. α: d 3.98. β: d 4.102, changes to α form at 1020C. Sublimes at 1180C. Soluble in acids; insoluble in water.

Использование

Pigment for paints, oilcloths, linoleum, leather, dental rubber, etc., especially in the form of lithopone; mixed with ZnO as "mineral white." Anhydrous zinc sulfide is used in x-ray screens and with a trace of a radium or mesothorium salt in luminous dials of watches; also television screens.

Методы производства

Production is similar to that of lithopone. A Na2S solution is mixed with a zinc salt solution under precisely controlled conditions. The resulting zinc sulfide precipitate is calcined and processed to give the finished product. Na2S + ZnSO4 →ZnS + Na2SO4.

Определение

zinc sulphide: A yellow-whitewater-soluble solid, ZnS. It occursnaturally as sphalerite (see also zincblende) and wurtzite. The compoundsublimes at 1180°C. It is used as apigment and phosphor.

Общее описание

A yellowish-white powder in a liquid. Insoluble in water and denser than water. Primary hazard is to the environment. Immediate steps should be taken to limit spread to the environment. Easily penetrates the soil to contaminate groundwater and nearby waterways.

Реакции воздуха и воды

Insoluble in water.

Профиль реактивности

These sulfides are rather inert, dissolve into acid, insoluble in water and alkalis.

Угроза здоровью

Inhalation of material may be harmful. Contact may cause burns to skin and eyes. Inhalation of Asbestos dust may have a damaging effect on the lungs. Fire may produce irritating, corrosive and/or toxic gases. Some liquids produce vapors that may cause dizziness or suffocation. Runoff from fire control may cause pollution.

Пожароопасность

Some may burn but none ignite readily. Containers may explode when heated. Some may be transported hot.

Промышленное использование

Zinc sulfide(Sachtolith) is mainly used in plastics. Functional properties such as lightening and hiding power are criteria for the use of Sachtolith. It has proved to be very useful for coloring many thermoplasts. During the dispersion process it does not cause abrasion of metallic production machinery or adversely effect the polymer, even at high operating temperatures or during multistage processing. Even ultrahigh molecular mass thermoplasts can be colored without problems. In glass-fiber-reinforced plastics, the soft texture of Sachtolith prevents mechanical fiber damage during extrusion. Sachtolith is also used as a dry lubricant during the fabrication of these materials.
The low abrasiveness of Sachtolith prolongs the operating life of stamping tools used in the manufacture of industrial rubber articles. The lightfastness and ageing resistance of many elastomers are improved by using Sachtolith. It is also used as a dry lubricant for roller and plain bearings, and as a white pigment for greases and oils.

Токсикология

The use of zinc sulfide and barium sulfate in contact with foods is permitted by the FDA (United States) and in most European countries. Some restrictions apply in France, Italy, the United Kingdom, and Czechoslovakia.
Soluble zinc is toxic in large amounts, but the human body requires small quantities (10–15 mg d−1) for metabolism. Zinc sulfide is harmless in the human due to its low solubility. The acid concentration in the stomach and the rate of dissolution following ingestion are not sufficient to produce physiologically significant quantities of soluble zinc. LD50 values in the rat exceed 15 g kg−1. No cases of poisoning or chronic damage to health have been observed in the manufacture of zinc sulfide pigments.