Zinc cadmium sulphide

In March 1963, after trials over Salisbury were inconclusive, Porton carried out the first in a series of zinc cadmium sulphide dispersion trials over the medium-sized city of Norwich in Norfolk. With the support of the... 

DERA 2000, pp. iiff. for a list of Porton s field trials with zinc cadmium sulphide see DERA 2000, pp. 16-23 Evans, R- 2000a, pp. 355ff. EUiot et al. 2002. 

TNA, WO189/1105, N. Thompson, A Comparison of Radio-Xenon and Zinc-Cadmium Sulphide Particle Tracers over Medium Distances ofTravef, PTP, No. 794 Mike Thompson and Jane Ray, BBC Radio 4 programme The Secrets of the Icewhale , 12 September 2002 (). 

Academy of Medical Sciences to the ChiefScientific Adviser, Ministry of Defence, Report on the Zinc Cadmium Sulphide Dispersion Trials Undertaken in the United Kingdom between 1953 and 1964 (no place, 1999) . 

DERA, Zinc Cadmium Sulphide (Fluorescent Particles) Field Trials Conducted by the UK 1953-19 4 (HMG, 2000). 

E.g., zinc silicate and zinc cadmium sulphide (Firm 108), calcium halophos-phate N 83 white, WQ, GQ or TQ (Firm 147) Ijeuchtstoff ZS-Super (Firm 118). 

Yellow - chrome rutile yellow, cadmium sulphide/zinc sulphide... 

Sulphide-type phosphors are produced from pure zinc or cadmium sulphide (or mixtures thereof) and heating them together at about 1000 °C with small quantities (0.1-0.001 per cent) of copper, silver, gallium, or other salts, which are termed activators. 

Copper-activated zinc and cadmium sulphides exhibit a rather long afterglow when their irradiation has ceased, which is favourable for application in radar screens and self-luminous phosphors. 

Preparation of Metal Sulphides by an Exchange Decomposition Reaction. Precipitation with Ammonium Sulphide. Pour 2 ml each of solutions of iron(ll), manganese(II), zinc, cadmium, lead, antimony, and copper salts into separate test tubes. Add 2 ml of an ammonium sulphide solution to each tube. Note the colour of the formed precipitates. Write the equations of the reactions and the values of the solubility products of the sulphides of these metals (see Appendix 1, Table 12). Using the concept of the solubility product, explain the process of precipitation of sulphides under these conditions. 

Sulphides. Acquaint yourself with the solubility products of zinc and cadmium sulphides (see Appendix 1, Table 12). Prepare the sulphides of these metals from solutions of zinc and cadmium nitrates. What should be used as the precipitant—hydrogen sulphide or ammonium sulphide Note the colour of the precipitates and test their reaction with 1 N solutions of sulphuric and hydrochloric acids. 

Properties dependent on adsorption are not confined to conductivity. Luminescence of materials may be affected, as Ewles and Heap (7) have shown for the case of silica, for which the luminescent peak at 4000 A. was shown to be associated with the adsorption of the OID radical. Many workers have demonstrated the dependence of the contact potential on the adsorption of gases. For example, Brattain and Bardeen (8) have shown that the contact potential of germanium varies with the adsorption of water vapor. Photoconductivity may be dependent on the adsorption. For example, Bube has shown (9) that the adsorption of water vapor has a marked effect on the photoconductivity of cadmium sulphide. He concluded (10) that the effect was indirect surface changes affect the lifetime of the excess carriers, thus affecting the photoconductivity. Melnick (11), however, working with zinc oxide, has produced evidence that part of the photoconductivity in this case is directly associated with excitation from adsorption levels. 

In the case of the alkali and alkaline earth metals, the sulphate is the sole product with copper, lead, bismuth and antimony, the product contains the metal, formed by reduction of the sulphate by unchanged sulphide. In cases where the sulphate is unstable at the temperature of reaction, as with zinc, cadmium, aluminium, tin, chromium, iron, cobalt and nickel, the oxide is the final product. The action may be catalytically accelerated by the addition of triferric tetroxide, Fe304.2... 

The principal red and yellow pigments are Lead chromate chrome yellow, orange and red), zinc chromate zinc or buttercup yellow), barium chromate lemon yellow or yellow ultramarine) various products based on jerric oxide, hydrated (yellow) or anhydrous (red), both natural yellow and red ochres) and artificial Mars yellow, English red, etc.) red oxide oj lead minium or red lead) mercuric sulphide cinnabar, vermilion) antimony oxysulphide antimony cinnabar) cadmium sulphide cadmium yellow) basic lead antimonate Naples yellow). 

Potassium, sodium and calcium sulphides are applied externally to soften the skin by dissolving the epidermis in diseases such as psoriasis, acne and seborrhea. Mixtures of calcium or potassium polysulphides and thiosulphate behave similarly and are also depilatories. Another common hair remover is barium sulphide, mixed with starch or zinc oxide, whereas selenium suphide and cadmium sulphide are applied topically, in shampoos, to control dandruff. 

Zinc.—The chief ore of zinc is the sulphide. To convert it into the oxide, it is roasted on a flat hearth in a current of air 2ZnS + 302= 2ZnO + 2S02. The oxide is mixed with small coal (slack) and placed in cylindrical retorts of fireclay. These retorts have pipes of rolled sheet-iron luted to the open ends with fireclay they are packed into a furnace in tiers, and the temperature is raised to bright redness. The coal distils first, giving off coal-gas, which expels air from the retorts. When the temperature exceeds 1000% the zinc distils and condenses in the iron pipes. It happens that almost all zinc ores contain cadmium sulphide, which, like zinc sulphide, is converted into oxide by roasting and on distillation, the cadmium, which is the more volatile metal, distils over first and condenses in the outer portion of the tubes. These are untwisted and the metal removed with a chisel. 

The precipitates are CuS, dark brown Ag2S, black ZnS, white CdS, yellow HgS + Hg, black and HgS, black. Of these only zinc sulphide and cadmium sulphide dissolve in 6 N HC1. 

Zinc, cadmium or tin When any of these metals is added to an acid (preferably hydrochloric acid) solution of a titanium(IV) salt, a violet colouration is produced, due to reduction to titanium(III) ions. No reduction occurs with sulphur dioxide or with hydrogen sulphide. 

---