These men seldom use vitrifiable enamels, pigments being much more tractable and less costly.
Other minerals whose production may be found stated in detail in the annual volume on Mineral Resources of the United States Geological Survey are: natural pigments, felspar, white mica, graphite, fluorspar, arsenic, quartz, barytes, bromine.
Many substances were used as pigments: Pliny records white lead, cinnabar, verdigris and red oxide of iron; and the preparation of coloured glasses and enamels testifies to the uses to which these and other substances were put.
Another very excellent method of vulcanizing cut sheet goods consists in placing them in a solution of the polysulphides of calcium at a temperature of 140° C. Rubber employed for the manufacture of cut sheets is often coloured by such pigments as vermilion, oxide of chromium, ultramarine, orpiment, antimony, lamp black, or oxide of zinc, incorporation being effected either by means of the masticator or by a pair of rollers heated internally by steam, and so geared as to move in contrary directions at unequal FIG.
The normal animal pigments and closely allied pigments.
Haematogenous pigments are derived from the haemoglobin of the red blood corpuscles.
Various coloured pigments may be deposited in the tissues through damaged skin surface - note, for example, the well-known practice of " tattooing."
Many workers following certain occupations show pigmented scars due to the penetration of carbon and other pigments from superficial wounds caused by gunpowder, explosions, &c.
Zinc chloride solution readily dissolves the oxide with the formation of oxychlorides, some of which are used as pigments, cements and for making artificial teeth.
But of the pigments employed nothing very laudatory could be said until very recent times.
By careful selection and preparation of pate, glaze and pigments, Dr Wagener proved not only that the manufacture was reasonably feasible, but also that decoration thus applied to pottery possesses unique delicacy and softness.
Cuenot, in order to explain certain features in the hereditary transmission of coat colour in mice, postulated the hypothesis that the grey colour of the wild mouse (which is known to be a compound of black, chocolate and yellow pigments) may be due either to the interaction of a single ferment and three chromogens, or vice versa, to one chromogenic substance and three ferments.
These, however, may with propriety be regarded as but different names for the same pigmentary substance, the variations in the character of which are attributable to the different modes in which the pigments are manufactured.
By adding certain alkalies to the other ingredients used in the preparation of these pigments, the colour becomes indigoblue, in which case it is the litmus of the Dutch manufacturers.
These pigments primarily depend upon special acids contained in the thalli of lichens, and their presence may readily be detected by means of the reagents already noticed.
It is cut in the volcanic plateau, and its ragged broken walls, which are inclined at very steep angles, are of a richness of colouring that almost defies description, a colouring that is produced by the action of the thermal springs, at the base of the canyon, upon the mineral pigments in the lava.
Many of the coloured pigments of fungi are fixed in the cell-walls or excreted to the outside (Peziza aeruginosa).
Copper carbonate is also the basis of the valuable blue to green pigments verditer, Bremen blue and Bremen green.
When the swollen wall is dense and regular in appearance the term " capsule " is applied to the sheath as in Leuconostoc. Secreted pigments (red, yellow, green and blue) are sometimes deposited in the wall, and some of the iron-bacteria have deposits of oxide of iron in the membranes.
W.) to liquefy gelatine, to secrete coloured pigments, to ferment certain media with evolution of carbon dioxide or other gases, or to induce pathological conditions in animals.
In the case of the scarlet and crimson red pigments of B.
Janthinus, &c., the redpurple of the sulphur bacteria, and indeed most bacterial pigments, solution in water does not occur, though alcohol extracts the colour readily.
In many cases the colour-production is dependent on certain definite conditions - temperature, presence of oxygen, nature of the food-medium, &c. Ewart's important discovery that some of these lipochrome pigments occlude oxygen, while others do not, may have bearings on the facultative anaerobism of these organisms.
They collect and spin the indigenous cotton, which is of good quality, and dye it with indigo or other pigments; they also manufacture very handsome shawls.
See Pigments and Mercury.