Lead sesquioxide

Lead Sesquioxide. Lead sesquioxide (lead trioxide), Pb202, is an amorphous, orange-yeUow powder soluble ia cold water. It decomposes ia hot water and ia acids to lead salts plus Pb02. Lead sesquioxide can be prepared from lead dioxide by hydrothermal dissociation (43). 

Lead sesquioxide is used as an oxidation catalyst for carbon monoxide ia exhaust gases (44,45) (see Exhaust control), as a catalyst for the preparation of lactams (46) (see Antibiotics, P-lactams), ia the manufacture of high purity diamonds (47) (see Carbon, diamond-natural), ia fireproofing compositions for poly(ethylene terephthalate) plastics (48), ia radiation detectors for x-rays and nuclear particles (49), and ia vulcanization accelerators for neoprene mbber (50). 

Synonyms lead sesquioxide dilead trioxide plumbous metaplumbate... 

It is stated that protoxide of mercury ia occasionally adulterated -with minium or red lead, sesquioxide of iron, and powdered brick. Such substances are readily detected by heating the substance to a dull heat the protoxide of meroury sublimes, and leaves the nonvolatile matters in the crucible, or the mercurial compound maybe treated with dilute nitric add, to dissolve the mercurial oxide and should minium be present, a pace-colored binoxide of lead remains together with the other adulterants, if any be present. On adding dilute sulphuric acid to the door liquor obtained in the foregoing, a white precipitate of sulphate of lead falls, corroborative of the existence of a lead compound. 

The dioxide. PbiO. has rutile structure, and the compound is a strong oxidizing agent. It is also amphiprotic. giving unstable lcad(IV) salts with acids, and orthoplnmbates. M PbOa, or metuplumbates. M PbO.. upon fusion with alkalies. Lead dioxide dissolves in aqueous alkali with formation of the ion Pb(OH)6. the alkali salts of which are isomorphous with the corresponding stannates and platinates. Lead sesquioxide, PbiO,. has been shown not to exist as a stable phase. 

The element forms stable oxides where the metal is in either lower oxidation state (lead oxide, PbO, commonly known as lithage) or the higher oxidation state (lead dioxide Pb02) or both (lead sesquioxide, PbjOg, and triplumbic tetroxide, Pb304, commonly known as red lead). These last two may be considered as mixtures of PbO and PbO,. 

Bingham, E., Pfizer, E.A., Barkley, W., Redford, E.P., 1968. Alveolar macrophages reduced numbers in rats after prolonged inhalation of lead sesquioxide. Science 162, 1297—1299. Bunn, T.L., Marsh, J.A., Dietert, R.R., 2000. Gender differences in developmental immunotoxi-city to lead in a chicken analysis following a single early low-level exposure in ovo. J. Toxicol. Environ. Health A 61, 677—693. 

Gasgnier M (2000) Ultrasound effects on metallic (Fe and Cr) iron sesquioxide (a-, y-Fe203) calcite copper, lead and manganese oxides as powders. Ultrason Sonochem 7 25-39... 

The oxide of lead which is used in the manufacture of crystal, is sot the protoxide commonly known as massicot, and represented by the formula Pb O, but minium, which is a sesquioxide, Pba 0 for, as Bahru el remarks, one may depend on tho latter net being mixed with metallic lead, which almost necessarily happens with the massicot of commerce. The object of employing oxide of lead in this kind of glass is to increase the density, and, consequently, tho refractive power, which gives the glass a peculiar lustre or brilliancy. 

B. C. Dutt and S. N. Sen found that when nitric oxide is passed into a suspension of barium dioxide in water, barium nitrite, not nitrate, is formed. P. Sabatier and J. B. Senderens observed no change when nitric oxide is passed over Cuprous Oxide at 500°. H. A. Auden and G. J. Fowler observed that dry nitric oxide and Silver oxide, at ordinary temp., form silver and silver nitrate P. Sabatier and J. B. Senderens also obtained silver and silver nitrite by passing nitric oxide into water with silver oxide in suspension. C. F. Schonbein found gold oxide is reduced by moist nitric oxide, forming nitrous acid. P. Sabatier and J. B. Senderens found that titanium sesquioxide forms white titanic oxide when heated in an atm. of nitric oxide and that stannous oxide below 500° burns in an atm. of nitric oxide, forming stannic oxide. If nitric oxide be passed into water with lead dioxide in suspension, the water is coloured, and in about 3 hrs., lead nitrite and nitrate are formed, and later, rhombic crystals of a basic nitrite. B. C. Dutt and S. N. Sen said that the nitrate is formed by the action of the dioxide on the nitrite. Lead dioxide is reduced to lead oxide by nitric oxide at 315°, and H. A. Auden and G. J. Fowler found that the reaction begins at 15°, when a basic lead nitrite is... 

The structure of platinum dioxide and its reactions with some di, tri, and tetravalent metal oxides have been investigated. Ternary platinum oxides were synthesized at high pressure (40 kUobars) and temperature (to 1600°C). Properties of the systems were studied by x-ray, thermal analysis, and infrared methods. Complete miscibility is observed in most PtO2-rutile-type oxide systems, but no miscibility or compound formation is found with fluorite dioxides. Lead dioxide reacts with Pt02 to form cubic Pb2Pt207. Several corundum-type sesquioxides exhibit measurable solubility in PtOz. Two series of compounds are formed with metal monoxides M2PtOh (where M is Mg, Zn, Cd) and MPt306 (where M is Mg, Co, Ni, Cu, Zn, Cd, and Hg). 

The raw material should contain at least 50 per cent, of Ca3P208 and be as free as possible from sesquioxides. It may be ignited if high in organic matter, reduced to a fine powder, and fed continuously into tanks lined with wood or hard lead alloy, where it meets on the counter current principle hot sulphuric acid of about 5 per cent, concentration. The reaction is quickly completed and the precipitated calcium sulphate is allowed to settle and filtered off continuously through filter presses. This sulphate is phosphatic gypsum and contains 3 to 4 per cent, of phosphoric acid of which 1 per cent, is soluble in water. The solution is evaporated in wrought-iron pans up to a concentration of 50 per cent, phosphoric acid, which may be further refined for use in pharmaceutical products or foods. 

---