Brown discolouration

Evidence for metals (e.g. iron, copper, tin, silver, etc) causing stain formation appears to be significant only for individuals exposed to metals and their salts, typically in connection with their occupation or certain medicines [140, 147], Stannous-fluoride-containing toothpastes have been reported to promote golden brown discolourations [63], The mechanism for stain formation probably involves interaction of dietary chromogens and metal ions forming coloured complexes on the tooth surfaces, as indicated by in vitro and in vivo studies [159,161]. 

May deep brown discolouration of the sea was reported by fishermen four miles off Blyth and ten miles ENE of Tynemouth. Plankton in the North Sea is regularly monitored by recorders which are routinely towed by merchant ships. These revealed a... 

PVC degrades rapidly in heat and fight unless it is effectively stabilised. The most obvious effect of degradation is discolouration initially yellowing but ultimately blackening. It is widely used in roof-lights and the formation of brown discolouration is the initial indication that the useful properties of the plastic (particularly impact resistance) are also deteriorating. Nevertheless, even transparent PVC can be made relatively durable to the outdoor environment by the use of or-... 

Regarding the stability of infusion vehicles only glucose 5 % has to be mentioned. Glucose 5 % infusion solutions should have a pH lower than 5.5 before sterilisation. Higher pH values cause yellow or brown discolouration and formation of cytotoxic degradation products such as 3-desoxyglucosone, 3,4-dideoxyglucosone-3-ene, formic acid, 5-hydroxymethyl-2-furfural, acetaldehyde [37]. 

Aldehyde-sugars (glucose) and derived disaccharides of it (lactose) in solid form are, in contrast to the keto-sugars (fructose), incompatible with strongly alkaline compounds and primary amines (ethylenediamine). A brown discolouration (caramellisation) takes place. In the case of primary amines is this called the MaUlard reaction. In mixtures of solid (anhydrous) substances these reactions proceed very slowly and they occur only on the surface of the sugar particle. Thus they may be irrelevant in practice. However, because of this incompatibility the WHO formulation for the oral rehydration salts prescribes anhydrous glucose, which moreover is not combined with sodium bicarbonate but with sodium citrate. It is preferable not to use lactose in capsules with primary aliphatic amines. A more recently reported Maillard reaction is that between lactose and fluoxetine [30]. 

Macroscopically, the cerebellum was the area of the brain most severely affected, although damage was seen in the cerebral hemispheres. A reddish brown discolouration was the most obvious change in the cerebellum, and... 

N-(l-naphthyl)-ethylenediamine dihydrochloride (NED, manual method) 0.5g of the amine dihydrochloride is dissolved in 500 mL of pure water. The solution should be stored in a brown bottle at < 8 °C. The reagent is stable for more than a month and can be used until a brown discolouration occurs. 

Unalloyed ferrous materials are used without additional protective measures to a strictly limited degree. The reason for their limited use is the lack of resistance of these materials to local attack, such as wide or deep pitting. In domestic installations, it is the brown discolouration and change in taste of drinking water (rusty water), above all, which are unacceptable to the public - although they are not a health hazard. 

Pipes made of unalloyed ferrous material, that is to say, cast iron and steel pipes, are used for strength in long-distance pipelines, because of the larger pipe dimensions and the high pressures. Unalloyed steel and cast iron materials are protected by linings because of the possible brown discolouration due to even relatively small amounts of iron dissolving out into the drinking water. 

Hindered phenols are known to be very effective at minimizing postirradiation embrittlement, but usually at the expense of unacceptable yellow-brown discolouration (3,5). The coloration is generally believed to result from the formation of products such as stilbene quinones (8-9). 

Reddish-brown discolouration of the urine of a patient taking levodopa 4 g daily was found to be due to contact with chlorine bleach used to clean the toilet bowl. The test was repeated in vitro on the urine of several patients (59). 

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