Lead dioxide color

CH2)2L0) were prepared. - " Such compounds can be oxidized with lead dioxide to N-picryl-9-aminocarbazyls (133). These black species are dehydrogenating agents though stable in dry chloroform the transformation of violet-black color into orange in benzene solution suggests that they... 

More definite evidence for the transient existence of the un-cyclized l-(jS-aminoethyl)-3,4-benzoquinones has been obtained recently by Kodja and Bouchilloux,77 78 who noted that a transient yellow color (Amax ca. 385 mp) was occasionally observed during the enzymic oxidations of catecholamines (particularly in unbuffered systems at low temperatures). This phenomenon was probably due to the formation of the transient o-quinones. (The absorption maximum of o-benzoquinone, the effective chromophore of the open-chain quinones, is known to occur at ca. 390 mp.79) An absorption maximum at 390 mp is characteristic of the formation of the dopa-quinone chromophore during oxidation of small C -terminal tyrosine peptides in the presence of tyrosinase.37 48 Similar spectroscopic features were observed when the oxidations were carried out with lead dioxide in sulfuric acid solutions (pH> 1). If the initial oxidation was carried out for a short period of time, it was possible to regenerate the original catecholamines by reduction (e.g. with sodium bisulfite, potassium iodide, and zinc powder) and to show that the 385 mp peak disappeared.77,78 Kodja and Bouchilloux were also able to identify 2,4-dinitrophenylhydrazones of several of the intermediate non-cyclized quinones by paper chromatography and spectroscopy (Amax n weakly acid solution ca. 350 mp with a shoulder at ca. 410 mp).77,78... 

NH2.K803 and (iii) the aq. soln. of the iso-salt is not coloured bluish-violet when treated with lead dioxide, or silver oxide, whereas the aq. soln. of the ordinary salt gives a coloration. F. Raschig also showed that (iv) the iso-salt is not hydrolyzed so readily as the ordinary salt and (v) whilst the potassium iso-salt separates from hot acidified soln. in anhydrous crystals, those of the ordinary salt are dihydrated. 

Dioxides. To about 1 gram each of manganese dioxide, Mn02, and lead dioxide, Pb02, in separate test tubes add 10 cc. of water and 5 cc. of 6N H2S04 or HNOa and warm for a few moments. Note that the dark-colored powders do not dissolve or change their appearance in any way, nor is there any effervescence. Filter off the insoluble powder and add titanium sulphate to the filtrate. Note that there is no yellow coloration. 

Chlorine from Hydrochloric Acid. Place about 0.5 gram each of manganese dioxide, lead dioxide, sodium dichromate, and potassium permanganate in separate test tubes. Add about 2 cc. of 6 N hydrochloric acid to each and test for chlorine by holding iodide-starch paper in the mouths of the tubes. Also after warming a very little observe the odor and color of the gas. Rinse out the tubes immediately at the sink under the hood. Compare the action of the oxides used above with that of copper oxide CuO and lead oxide PbO. 

Since 2,4,6-triphenylphenol can be easily oxidized to a stable radical, we were interested in the behaviour of various substituted 2,4,6-triphenylbenzenes. When Schromm 140) oxidized 2,4,6-triphenyl-aniline by shaking a solution in benzene with lead dioxide, no radical was detected either by ESR spectroscopy or by trapping with tri-phenylmethyl. A red color (A. = 520 nm) possibly due to the ArNH radical was, however, observed.,40>. The addition of 70% perchloric acid changes the color to deep blue-violet. The compound was isolated when a benzene solution of 2,4,6-... 

Lead can be determined odlorlmetrlcally by electrolytic deposition as dioxide followed by oxidation of tetra-methyldlamlnodlphenylmethane by the dioxide to an Intensely colored blue dlphenylmethane dye (S5) It. may be used for amounts of lead above 5/. This method would appear to have limited application. However if an electrodeposlted lead dioxide deposit Is used as a method of mounting a lead sample, for measurement of Its radioactivity this may be a useful method of subsequently determining Its lead content. 

To date, the most frequent application of Ebonex (named for its black color) has been in cathodic protection, especially of the steel rods used to reinforce concrete [1]. There is an extensive literature oti Ebonex coated with various other materials (noble metals, carbon, lead dioxide), whose deposition is favored by Ebonex s high overpotential for hydrogen and oxygen evolution. Applications for coated Ebonex include batteries, fuel cells, and dechlorination of chlorinated pollutants [2], but the focus of this article is the use of uncoated Ebonex as an electrode material for electrolysis of pollutant substances, most often for electrochemical oxidation. 

UPRs based on a mixture of maleic anhydride, phthalic anhydride and adipic acid in a molar ration of 1 2 2 were prepared in the presence of the polyesterification catalysts, i.e. lead dioxide, p-toluenesulfonic acid monohydrate and zinc acetate dihydrate, and next crossHnked with styrene by using MEKP as the initiator and cobalt naphthenate (CoNp) as the promoter [197]. Most often, the catalysts used in the polyesterification process cannot be easily separated from the polyester, thus the effect of the residual catalysts on the curing process and color of the cured polyester resin should be taken into account. It was shown that the residual catalyst could affect the curing reaction even in a small amount (Table 28), increasing the activation energy a, frequency factor ko and the reaction order x. 

At least six specifications of standards for granulated sugar quaUty are appHcable ia the United States. These include Codex JUimentarius Food Chemicals Codex (ECC) (4), US. Pharmacopeia (USP) and National Formula (NE) (5), National Soft Drink Association (6), National Canners Association, and Mihtary Standard-900 for white sugar. These standards are intended to set limits on various components, including, but not necessarily limited to, polarization, invert or reducing sugar, ash, moisture, color, sulfur dioxide, arsenic, lead, and copper. 

Lead, arsenic, and antimony—determined in the solution obtained by boiling 10 g of the titanium dioxide for 15 min in 50 mL of 0.5 Nhydrochloric acid In addition to individual specifications, general specifications have been written for provisionally Hsted certifiable colors ... 

---