Gas leaves the retorts saturated with naphthalene, and its capacity for holding that impurity seems to be augmented by the presence of water vapour.
There was also associated in the Hebrew mind a connexion of impurity and corruption with the notion of leaven which was tabu in all sacrifice (Exod.
It is a mirror which no stone can crack, whose quicksilver will never wear off, whose gilding Nature continually repairs; no storms, no dust, can dim its surface ever fresh;--a mirror in which all impurity presented to it sinks, swept and dusted by the sun's hazy brush--this the light dust-cloth--which retains no breath that is breathed on it, but sends its own to float as clouds high above its surface, and be reflected in its bosom still.
In Judaism, as in other, especially Oriental, religions, the natural dislike of material defilement has been elevated into a religious sentiment, and made to support a complicated system of quasi-sanitary abstinences and ceremonial purifications; then, as the ethical element predominated in the Jewish religion, a moral symbolism was felt to reside in the ceremonial code, and thus aversion to impurity came to be a common form of the ethico-religious sentiment.
Vatke considered it a celebration of the spring solstice, Baur a means of removing the impurity of the old year.
This agrees with the well-known fact that the presence of an impurity in a substance depresses its melting-point.
It is he, therefore, who is called upon to cleanse the sick and suffering from disease, which, superinduced by the demons, was looked upon as a species of impurity affecting the body.
Small quantities of the iodate (KIO 3) are a frequent impurity in iodide of potassium, and cause the congeries of symptoms known as iodism.
Hence any impurity which diminishes the surface tension of the water will diminish the size of the drop (unless the density is proportionately diminished).
Nevertheless, it has been found in practice, when syrups with low quotient of purity and high quotient of impurity are being treated, injecting the feed at a number of different points in the pan does reduce the time required to boil the pan, though of no practical advantage with syrups of high quotient of purity and free from the viscosity which impedes circulation and therefore quick boiling.