Substances, colourless observable

Lawson " found that aconitine was converted by nitrous acid into a substance, C3jH40Oj2Nj, crystallising in small, colourless prisms, m.p. 276° (dec.). Jacobs and Craig confirmed this observation but prefer the formula C34H44O13N2. Nitric acid converts this nitroso-derivative into the nitronitroso-compound, 0311135013X3, described above. 

Coloured substances can be observed visually in situ after development of the chromatogram, but those which are colourless must be visualized by physical or chemical means. For many samples, and especially for... 

Schmidlin s experiment here described shows very clearly the equilibrium between hexaphenylethane and triphenylmethyl. The disappearance of the colour on shaking the substance with air indicates that the yellow radicle, present in equilibrium, is removed as (colourless) peroxide. The re-establishment of the equilibrium by renewed dissociation of (colourless) hexaphenylethane proceeds so slowly that the formation of the yellow radicle in the decolorised solution can be observed without difficulty. 

In 1962, it was reported that when silver nitrate was added to a warm aqueous solution of acacenH2, a finely divided colourless compound immediately precipitated. If instead the solution was heated on a water bath, then an uncharacterized dark brown substance formed. Analytical data and conductivity measurements suggested that the former complex was Ag2(acacenH2)(N03)2.391 The decomposition observed was most likely caused by hydrolysis, since many Schiff base ligands hydrolyze rapidly in water. 

Mechanisms ascribed to class 2 can be called those with "colourless steps (i.e. those containing no observed substances). 

Borax bead reactions (T able V.7.) Prepare a borax bead in a loop of platinum wire by dipping the hot wire into borax and heating until colourless and transparent. Bring a minute quantity of the substance into contact with the hot bead and heat in the outer or oxidizing flame. Observe the colour when the bead is hot and also when it is cold. Heat the bead in the inner or reducing flame and observe the colours in the hot and cold states. Coloured beads are obtained with compounds of copper, iron, chromium, manganese, cobalt, and nickel (see however, Section VII.25, Table VII.8). ... 

Pure anhydrous hydrocyanic acid is a clear colourless liquid with a peculiar odour which is usually compared with that of bitter almonds. It has been observed, however, that this substance has an indefinite odour which varies with the degree of its dilution with air and the period of exposure to it. ... 

One part of ergotamine is suspended in 10 parts of hydrazine hydrate and heated in a nitrogen atmosphere at 100° C. The substance becomes dissolved very rapidly, but as soon as complete dissolution has occurred, precipitation of a solid, nearly colourless compound takes place. The analysis of a test taken out shows that under the action of hydrazine, ergotamine has been transformed into the difficultly soluble ergotaminine. The suspension is then heated further and after about 20 hours it can be observed that complete dissolution has taken place. The brownish solution is then concentrated in vacuo to about 5 parts, whereby the lysergic acid hydrazide begins to separate out in the form of a crystalline greyish powder. In order to complete the precipitation, the reaction mass is left to stand for 1 to 2 days in a cool place in order to complete the crystallization. After this time the crystals are filtered and washed with some absolute alcohol. Yield 0.26 parts, which corresponds to 68 per cent, of the theoretical. 

The calcium carbonate equihbrium was one in which nineteenth-century scientists had to revise their apparent observation that only two phases—a white solid and a colourless gas— where involved because this wasn t consistent with a variance of one in the light of the phase rule. Usually the number of phases is a straightforward matter. But this still leaves several variables, often raising questions of interpretation which must be addressed before the number of substances present in a mixture can be determined from an application of the phase rule. Such interpretation usually calls on ideas about distinctions of substance drawn from other quarters. The microscopic realm is an obvious source, but as we will see, the idea of molecular stmcture is equally one which doesn t stand on its own feet. The notion of sameness of substance is an eclectic affair involving diverse theoretical inputs. A simple, unproblematic, universal criterion of sameness of substance is something of a pipedream. 

Saponins. These haemolysing substances are detected by contact with a blood-gelatine solution on the plate [89 a, 251, 324, 328] haemo-lytical halos are observed. These zones, where the saponins have diffused out of the chromatogram are, transparent and almost colourless in contrast to the normally cloudy and red blood-gelatine layer. 

The macroscopic domain (hereinafter shortened to macro domain) mainly deals with substances and chemical phenomena that can be observed, smelled, and so on. For instance, sodium chloride (the main component of table salt) will be described as a white or colourless crystalline solid with a characteristic taste and the property to dissolve in water. 

Benzothiazolyl-lithium (70), prepared from benzothiazole and n-butyl-lithium in THF at —80 C, reacts in situ with the appropriate chlorosilanes to afford mono- (71) and di-(2-benzothiazolyl)silanes (72) (see also these Reports, Vol. 2, p. 672). The latter are also formed in higher yields from (71) by a novel trans-silylation reaction. The assigned structures of the silylbenzothiazoles are in agreement with their observed n.m.r. spectra. The compounds are colourless, stable substances, of considerable reactivity. 

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