It crystallizes in colourless prisms and is optically active.
Lehmann it melts at 168° (or at a slightly lower temperature in its water of crystallization) and on cooling forms optically isotropic crystals; at 125.6° the mass becomes doubly refracting, and from a solution rhombohedral (optically uniaxial) crystals are deposited; by further cooling acicular rhombic crystals are produced at 82.8°, and at 32.4° other rhombic forms are obtained, identical with the product obtained by crystallizing at ordinary temperatures.
Since the molecule contains an asymmetric carbon atom, the acid exists in three forms, one being an inactive "racemic" mixture, and the other two being optically active forms. The inactive variety is known as paramandelic acid.
The osazone prepared from a-acrose resembled most closely the glucosazone yielded by glucose, mannose, and fructose, but it was optically inactive; also the ketose which it gave after treatment with hydrochloric acid and reduction of the osone was like ordinary fructose except that it was inactive.
7 and 8 can be at once ruled out, however, as acids so constituted would be optically inactive and the saccharic acids are active.
If the configuration of d-saccharic acid were given by either 6 or To, bearing in mind the relation of mannose to glucose, it would then be necessary to represent d-mannosaccharic acid by either 7 or 8 - as the forms 6 and Io pass into 7 and 8 on changing the sign of a terminal group; but this cannot be done as mannosaccharic acid is optically active.
Hence it follows that the " optical " formulae of the acids derived from two pentoses having the configuration given above will be C02H - 0 - C02H CO 2 H + 0 - C02H, and that consequently only one of the acids will be optically active.
When oxidized this aldohexose is first converted into the monobasic galactonic acid, and then into dibasic mucic acid; the latter is optically inactive, so that its configuration must be one of those given in the sixth and seventh columns of the table.
A standard 128 Efork could then be compared either optically or by beats with the electrically driven fork.
The temperature is uniformly 54° Fahr., and the atmosphere is optically and chemically pure.
It is optically active, the natural form being laevorotatory.
The substance is usually optically isotropic, though sometimes it exhibits anomalous double refraction; fibrous zinc sulphide which is doubly refracting is to be referred to the hexagonal FIG.
VALERIC ACID, or [[Valerianic Acid, C4h9 C02h]], an organic acid belonging to the fatty acid series, which exists in four isomeric forms, one of which contains an asymmetric carbon atom and consequently occurs in two optically active modifications and one optically inactive modification.
CH 2 CO 2 H, and optically active methylethylacetic acid, (CH 3) (C 2 H 5)CH CO 2 H, which occur free or as esters in the vegetable and animal kingdoms, chiefly in the roots of Angelica archangelica and Valeriana officinalis.
One line, in the yellow green, is so dominant optically as often to be described as the auroral line.
Two points are selected on the surface of the shaft at different positions along it, and the relative displacement which occurs between them round the shaft when power is being transmitted is determined either by electrical means, as in the Denny-Johnson torsion-meter, or optically, as in the Hopkinson-Thring and Bevis-Gibson instruments.
W.) hydrogen result; Micrococcus acidi-paralactici, on the other hand, ferments such solutions to optically active paralactic acid.
The surface region which yields a continuous spectrum is called the photosphere; it possesses optically a sharp boundary, which is generally a perfect sphere, but shows occasionally at the rim slight depressions or more rarely elevations.
It occurs in two optically active forms, namely, as laevo-asparagine and dextro-asparagine.
It may be safely said of all those living things which are large enough to enable us to trust the evidence of microscopes, that they are heterogeneous optically, and that their different parts, and especially the surface layer, as Life and contrasted with the interior, differh sicall and organiza- P Y ?
He was a strong advocate of the groupflashing system as a means of differentiating lights, and invented an arrangement for carrying it into effect optically, his plan being first adopted for the catoptric light of the Royal Sovereign lightship, in the English Channel off Beachy Head.
It is, in fact, admitted that some of the glasses, most useful optically, the dense barium crown glasses, which are so widely used in modern photographic lenses, cannot be produced entirely free either from noticeable colour or from numerous small bubbles, while the chemical nature of these glasses is so sensitive that considerable care is required to protect the surfaces of lenses made from them if serious tarnishing is to be avoided.
The reason for this high cost is to be found partly in the fact that the yield of optically perfect glass even in large and successful meltings rarely exceeds 20% of the total weight of glass melted.
Their solutions are optically active, i.e.
If the nitrogen atom in the quaternary ammonium salts be in combination with four different groups, then the molecule is asymmetrical, and the salt can be resolved into optically active enantiamorphous isomerides.
The corresponding iodides are obtained by the addition of potassium iodide to solutions of the sulphonates, and are optically active antipodes.
There are a number of optically bright lines of longer wavelength.
Atropine is optically inactive; hyoscyamine, possibly a physical isomer, which yields atropine when heated to 108.6°, is laevorotatory.
Succeeded in mounting them with all necessary rigidity free from flexure but have given them optically true plane surfaces, notwithH standing their large diameters, viz., II and 15.7 in.
It is optically active - a fact taken account of in J.
Throughout the year, and the atmosphere is both chemically and optically of singular purity.
In crystals the rotary property appears to be sometimes inherent in the crystalline arrangement of the molecules, as it is lost on fusion or solution, and in several cases belongs to enantiomorphous crystals, the two correlated forms of which are the one right-handed and the other left-handed optically as well as crystallographically, this being necessarily the case if the property be retained when the crystal is fused or dissolved.
This is valid so long as the pencil is in air; but if, on the other hand, the pencil passes from air through a plane surface into an optically denser medium, e.g.
An instrument for exhibiting optically or graphically these variations is called an oscillograph, or sometimes an ondograph.
The oscillograph can be made to exhibit optically the form of the current curve in non-cyclical phenomena, such as the discharge of a condenser.