Nitrate occlusion

For solutions containing sulphuric acid or a sulphate the reagent commonly applied is barium chloride, both when the test is to be qualitative and when quantitative. Precipitation is effected by the gradual addition of barium chloride to the boiling solution containing a little hydrochloric acid, but for the production of pure barium sulphate, and therefore in order to ensure accuracy, certain precautions must be observed.4 Nitrates, perchlorates, phosphates, tervalent metals and large quantities of salts of the alkali metals (particularly potassium) and of the alkaline earth metals are to be avoided, as they cause the precipitated barium sulphate to be rendered impure by occlusion of otherwise soluble substances.5 Such impurities may be accounted for partly by... 

Similar observations were also published earlier by Tribot and Marsaudon [16]. Recently, however, Lhoste [17] has questioned the validity of the hypothesis of the formation of sulphuric acid esters during the nitration of cellulose. On the basis of analytical data the author has arrived at the idea that sulphuric acid is bound with nitrocellulose solely by occlusion. He found no evidence to confirm the existence of cellulose sulphates in nitrocotton. 

Meyer H.Wehrli, Helv 20, 353(1937) CA 31, 5807(1937) 5)M.L.Wolfrom et al, JACS 65, 2084(1943) 6)M.L.Wolfrom et al, Ohio State Univ Final Rept, Project 459, Columbus, Ohio(Jan 1953)pp 1,3 34 Nitrated Deacetylated Chitine A wh flocculent ppt contg 11=6 to 11,9% nitrate N(as detd by DuPont nitrometer obtd by Wolfrom et al(Ref 3) by nitrating deacetylated chitin with 100% HNOj. The nitrated product represented the combined nitrate salt nitrate ester of deacetylated chitin. This substance contd one nitric acid salt unit per anhydro-o-glucosamine unit and 1.60-1.65 nitrate ester unit per anhydro-o-glucosamine anhydro -N-acetyl-D -glucosammine units. Attempts to nitrate deacetylated chitin by means of nitrogen pent oxide, in a non-aqueous medium y in the presence of sodium fluoride, by the method of Caesar(Ref 2) were unsuccessful mainly because of occlusion of NaF in the nitrated products(Ref 3)... 

Trace analysis has its special hazards for the unwary. The most important of these are loss of material in the analytical process and contamination by outside sources. Everyone realizes that trace constituents can be lost from samples, but few are aware of the many ways in which this can occur. For example, phosphate has been observed to disappear mysteriously from water samples in polyethylene bottles (10). Nitric acid, used to clean plastic vials, has been observed to convert these surfaces to ion exchangers, which readily take up as much as 10 12 moles per sq. cm. of trace metals (16). Lead nitrate solutions unless made distinctly acidic, plate out much of the lead on the walls of glass bottles. While everyone realizes that formation of a precipitate is liable to carry out trace constituents either by adsorption or occlusion, it is not as well-known that vanishingly small amounts of precipitates—amounts likely to be overlooked on casual observation—may also do this. The fly-ash and soot, which seem to be inescapable components of city air,... 

In his monograph (9), Rabo reported the first studies of solid-state reactions between zeolites, mainly Y zeolite, and some salts. These studies revealed either ion exchange or more or less reversible occlusion of the salt. In cases of occlusion, the salt anion (halide, nitrate, or oxygenated chlorine anions) was usually located in sodalite cavities. 

Fractional precipitation or dissolution of polysaccharides (and polysaccharide acetates or nitrates), either by changing the solvent composition, pH, or temperature, is generally of only limited application, except for the removal of extraneous material, because of the tendency to coprecipitation and occlusion of other polysaccharides. As most polysaccharides show considerable polymolecularity (that is, they have a broad molecular-weight... 

Nitrate and nitrites can combine with secondarys amines to form dimethylnitrosamines, which are acutely toxic and cause centrilobular necrosis, fibrous occlusion of central veins, and pleural and peritoneal hemorrhages in animals. In the body nitrates are converted to nitrites, which can oxidize hemoglobin to methemoglobin and lead to cyanosis. 

In the event of prolonged chest pain and ischemic ECG changes unrelieved by nitrate therapy or calcium channel antagonists, one may assume total occlusion of a coronary vessel, and steps should be taken to restore blood flow with either PCI or CABG. 

An alternative route to the occlusion of salts in zeolite systems is by means of high temperature reactions involving previously imbibed salts. This procedure has been successfully employed to fill the zeolite cages of X, Y and A zeolites with anions such as chloride, bromide, iodide, nitrate and chlorate (refs. 4,7). It offered a possible means of occluding the oxyanions of transition metals such as Cr, Mo and W in the sodalite cages of hydroxy-sodalite and zeolites. 

Oasil - Meprobamate Obaron - Benzbromarone Obe-Del Phendimetrazine tartrate Obepar - Phendimetrazine tartrate Obesan - Phendimetrazine tartrate Obestat Phenylpropanolamine HCI Obestin - Phentermine HCI Obetrol - Dextroamphetamine sulfate Obex-LA Phendimetrazine tartrate Obezine Phendimetrazine tartrate Oblioser - Methaqualone Obotan - Tanphetamin Obsidan Propranolol HCI Obstiiax - Bisacodyl Obstilex - Oxyphenisatin acetate Oby-Trim Phentermine HCI Occlusal - Salicylic acid Ocelina - Metampicillin sodium Oceral Oxiconazole nitrate Octapressin Felypressin Octtcair - Hydrocortisone Octicair - Neomycin Octicair Polymyxin Octinum Isometheptene Octocaine Lidocaine... 

Arthritic patients, elderly people and children all experience difficulties with administering eye drops [43, 134—137]. In the group of elderly persmis studied less than 33 % were able to instil eye drops or even to squeeze the dropper bottle. Only 50 % of the persons, who were able to administer their eye drops could apply the eye drops into the conjunctival sac. This illustrates that clear and practical instructions are required. For children clear instructions were described for an alternative method of administration. The technique was initially tested on volunteers (20-33 year old). The patients should lay down and close their eyes. The caregiver instils a drop on the inner canthus (near the nose), the patient then slowly opens their eye lids and the drop runs into the tear film. The pharmacological effect of pilocarpine nitrate 0.25 % and 0.5 % applied using the above described technique, exhibits an effect between that of pilocarpine nitrate 0.25 % and 0.5 % with nasolachrymal occlusion. The closed eye technique is thus an effective and easy to use alternative for reluctant children. 

Pistoia has used electrochemically generated nitrate radicals to effect the bulk polymerization of acrylonitrile the system shows a remarkable postpolymerization effect which is affected by such factors as the anode material, current, temperature, stirring, electrolysis time, and HNO, concentration. Radical occlusion phenoma and the formation of oligomers limit the monomer to >oly-mer conversion. Pistoia has also reported the polymerization of acrylonitrile by the oxidation of sulphuric acid at the anode and has extended the work to the anodic polymerization of methyl methacrylate in methanol-sulphuric acid... 

Although this coulometer gives very accurate results, there is the possibility of some occlusion of water or nitrate in the silver deposit. For this reason, the dissolution reaction was preferred in the most recent determination of the Faraday constant (q.v.). 

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