Phosphor advantages

The alicyclic secondary alcohol, cycZohexanol, may be dehydrated by concentrated sulphuric acid or by 85 per cent, phosphoric acid to cyciohexene. It has a higher boiling point (82-83°) than amylene and therefore possesses some advantage over the latter in.the study of the reactions of unsaturated hydrocarbons. 

Phosphoric acid method. The advantages of phosphoric acid as a dehydrating agent in this preparation are the absence of carbonisation and the freedom of the product from sulphur dioxide. 

Divalent europium-activated BaECl was the first rare-earth-activated x-ray phosphor (24). The advantage of BaECLEu " over the conventional CaWO material is in the higher x-ray absorption and better x-ray-to-visible light conversion. The problem with BaECl for x-ray appHcation is in the lower density (4.56 g/cm vs 6 g/cm for CaWO and plate-like morphology. 

Thermal polymerization is not as effective as catalytic polymerization but has the advantage that it can be used to polymerize saturated materials that caimot be induced to react by catalysts. The process consists of the vapor-phase cracking of, for example, propane and butane, followed by prolonged periods at high temperature (510—595°C) for the reactions to proceed to near completion. Olefins can also be conveniendy polymerized by means of an acid catalyst. Thus, the treated olefin-rich feed stream is contacted with a catalyst, such as sulfuric acid, copper pyrophosphate, or phosphoric acid, at 150—220°C and 1035—8275 kPa (150—1200 psi), depending on feedstock and product requirement. 

Acid Treatment. The treatment of petroleum products with acids has been in use for a considerable time in the petroleum industry. Various acids such as hydrofluoric acid, hydrochloric acid, nitric acid, and phosphoric acid have been used in addition to the most commonly used sulfuric acid, but in most instances there is Httie advantage in using any acid other than sulfuric. 

The acid process has three advantages over the alkaline process, ie, (/) higher yield of phosphine (60 vs 25%) (2) more pure gas for use in subsequent reactions (95 vs 40%) and (J) by-product phosphoric acid is relatively valuable and can be sold into a number of markets, eg, in the manufacture of fertilizers and flame retardants. There is no ready outlet for the mixture of phosphites produced via the alkaline route and additional processing by oxidative spray drying is needed to produce phosphates for sale (3). 

Zinc compounds are generally colorless unless the other component, eg, chromate, is colored. The lack of color of most zinc compounds in visible light is a great advantage in that they do not color paint films, plastics, mbber, cosmetics, etc. However, when excited by various types of radiation and at various temperatures, zinc oxide, sulfide, selenide [1315-09-9], and related compounds exhibit luminescence, ie, they emit colored light (see Luminescent materials). Zinc-based phosphors can be produced in many colors, depending upon the added dopants. They are used in television tubes, luminescent glasses, and various specialty products. 

Note Phosphoric acid [8] and hydrochloric acid [6, 9] have both been suggested in the literature as substitutes for phthalic acid. The addition of sodium dithionite [9] is also occasionally mentioned and sometimes no additives are employed [10]. The alternative reagents offer no advantages over the phthalic acid containing reagent since they usually cause more background coloration. The limits of detection are about 0.1 —0.5 pg per chromatogram zone [5]. 

The sulphuric acid, used to acidulate before distillation, may be advantageously replaced by phosphoric acid. This modification, whilst in many cases not absolutely essential, is desirable on account of the fact that sulphuric acid is liable to become reduced by certain constituents of oils, particularly of old oils, which frequently contain substances of a resinous nature. In such cases the volatile acid products of the reduction pass over along with the true acids of the oil undergoing examination. 

The main line of development now lies with its successor, the glass-ionomer cement, which uses a similar glass, but in which phosphoric acid is replaced by poly(acrylic acid) this cement is more resistant to acid erosion and staining and has the great advantage of adhesion to tooth material. 

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