Lead, extraction

In order to concentrate the lead extract, remove the lead from the organic solvent by shaking this with three successive 10 mL portions of the dilute hydrochloric acid solution, collecting the aqueous extracts in a 250 mL beaker. To the combined extracts add 5 mL of 20 per cent ascorbic acid solution and adjust to pH 4 by the addition of concentrated ammonia solution. Place the beaker in a fume cupboard, add 3 mL of the 50 per cent potassium cyanide solution and immediately adjust the pH to 9-10 with concentrated ammonia solution. Transfer the solution to a 250 mL separatory funnel with the aid of a little de-ionised water, add 5 mL of the 2 per cent NaDDC reagent, allow to stand for one minute and then add 10 mL of methyl iso butyl ketone. Shake for one minute and then separate and collect the organic phase, filtering it through a fluted filter paper. This solution now contains the lead and is ready for the absorption measurement. 

Lead Lead extracted from water with chloroformic dithizone Graphite furnace AAS - [364]... 

Boliden (2) A lead extraction process in which a sulfide ore, mixed with coke, is smelted in an electric furnace, air jets forming vortices between the electrodes. Discontinued in 1988 in favor of the Kaldo process, using a rotating furnace. 

Cominco [Consolidated Mining Smelting Company] A process for absorbing sulfur dioxide from smelting operations. The sulfur dioxide is absorbed in an aqueous solution of ammonium sulfite regeneration is by acidification with sulfuric acid. The ammonium sulfate byproduct is sold. Operated at the Cominco smelter at Trail, Canada, and at other smelters and sulfuric acid plants in the United States. Licensed by the Olin Mathieson Corporation. The name has been applied also to a lead extraction process. 

St. Joseph Also known as St. Joe. A process for extracting zinc from zinc sulfide ore by electrothermic reduction, practised by the St Joseph Lead Company at its Josephtown refinery in the United States, in the 1930s. A mixture of zinc blende with coke was heated by passing electricity through the mixture. The zinc vapor thus produced was condensed in a bath of molten zinc. The name has also been applied to a similar lead extraction process. 

Reference to Table III shows that in the presence of 0.83 m sodium chloride and for an aqueous-to-organic phase ratio Vaq/Vorg = 1.0, a ratio Cr/Cl of 1.0 is sufficient to remove at least 75% organic lead. For solvents such as benzene and chloroform this ratio is sufficient to achieve complete organic lead extraction. 

Continued analysis of Sasanian silver objects will be directed towards (1) a detailed statistical study of the data, (2) analysis of Sasanian and Umayyad coins, (3) determination of isotope ratios of lead extracted from the silver, (4) correlation between the analytical data and stylistic information obtained from an art historical and archaeological study and with information on methods of manufacture, toolmark, etc. 

Standing Committee of Analysts (DoE) (1979)The Analysis of Agricultural Materials -Lead, Extractable in Soil Method 43, MAFF Technical Bulletin RB 427, HMSO, London, UK. 

The selectivity of the Pb reaction with PAR can be increased by the use of cyanide, which efficiently masks Ag, Cd, Hg, Cu, Ni, Co, and Zn. Another way to improve the selectivity is to use a preliminary isolation of lead. Extraction as the iodide complex is a convenient method for its separation from interfering metals. Before this operation, Fe(III) and some other metals can be separated by extraction as thiocyanate complexes. Then potassium iodide is added, the HCl concentration adjusted, and the iodide-lead complex extracted with MIBK. Besides lead, the extract should contain only cadmium (see the procedure below). However, in the preliminary extraction from thiocyanate medium, about 15% of the lead present is also extracted [4]. 

The inertness of lead-stabilized PVC can be demonstrated by extraction studies. Eor instance, several studies have shown that the amount of lead extracted from lead-stabilized water pipes is negligible when tested according to the requirements of the EU plastics Directive (2002/72/EC) which specify the maximum amount of lead that can be extracted from plastics in contact with food which includes drinking water [148]. 

On the other hand several investigators have obtained a value of approximately 206 0 for lead extracted from pure uranium minerals. Mention may be made of the value 206 06 obtained by Hfinigschmidt and Horovitz in 1915 for lead from a sample of Norwegian brfiggerite, a variety of uraninite from Norway and 206 00 found by Baxter in 1933 for lead from Katanga pitch-blende. The atomic weight of ordinary lead is 207 22. 

Silver is the most important metal in the photographic industries and its complete recovery from the photographic waste stream is very desirable from the points of view of saving resources and preserving the environment [83]. Selective transport or extraction of Pb ions is also of interest in relation to the environmental and human toxicity [84]. We were thus stimulated to synthesize some crownophanes possessing alkylthio-, picolyl- or carboxyl-groups in the side chains, expecting them to exhibit such silver and lead extraction abilities. 

Over 95% of failed lead—acid batteries are recycled in these pools, yielding secondary lead which is re-used for the manufacture of new lead—acid batteries. The secondary lead is purified to a degree, allowing its utilization in the production of leady oxide and lead alloys. A certain amount of primary lead extracted from lead ores is also added to the lead pool and used in the manufacture of leady oxide. Thanks to the high percentage of recycled secondary lead and the simple technology of manufacture, the lead—acid battery is the cheapest chemical power source available. 

Lead (Pb) compounds, the deadly cumulative poison indoors, can leach from old water pipes (in the form of soluble lead), and from badly glazed pottery, and even from lead crystal decanters. In a study, it was shown that the rate of lead extraction from a 100 mm diameter PVC waste water pipe system was 0.7 pg [26] and that the sewer system can contribute 0.5 pg/l/lead to the wastewater [27], On the other hand, in the CSIRO report it is concluded that, under normal use conditions in the potable water industry, the level of lead extracted from properly commissioned PVC pipe has been found to be below the levels of detection [27]. 

Lead extraction fiom battery paste by smelting requires the addition of fluxes and a high temperature (1100 °C or above) for the decomposition of the lead sulphate. The inconvenience that such a high temperature entrains is well understood. On the contrary, smelting operations would be substantially simplified if sulphate-free lead oxide materials could be treated. 

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