Ether can be boiled in a vessel immersed in water, because it boils at a lower temperature, 960.

Water is best kept in uncovered cisterns, because the air prevents or annihilates putrefaction by supplying it with oxygen. It should never be allowed to stagnate; the water in the cistern should be drawn off and replaced every twenty-four hours if possible.

But do not leave a cistern or tank of water uncovered near any offensively smelling objects - if it is in the scullery or near a dung or dirt heap have it covered, but draw it off frequently, and have the cistern cleaned out every six months at the very least.

Boiling water is an admirable way of purifying it, but as it becomes very flat afterwards by losing its carbonic acid, aerate it again by pouring it at as great a height as you can from one jug to another six times. It will then be fresh and sparkling.

The temperature at which water is drank, is of importance in a sanitary point of view. Below 450 it is an astringent: at 6o° a diluent, and of use for removing indigestion; a celebrated gourmand of the Regency was accustomed to drink a wine-glass of water at 60o after his dinner daily.

Water of a temperature from 700 to 8o°, drunk the first thing in the morning, is an excellent antibilious dose. Water is cold at 8o° to the hand; it is tepid from 86° to 90° at 100° it is warm, at 212° boiling.

The following are some of the tests for water: - Proportion a few drops ' of the one used to a wine-glass or tumbler of water.

To detect alkaline carbonates and sulphates - a solution of nitrate of barytes. If they are in the water it will cause a turbid appearance.

To precipitate lime: - a solution of oxalate of ammonia.

Free carbonic acid is detected by an appearance of milkiness when an equal quantity of lime water is added to the water tested. Magnesium waters possess the look and properties of magnesia. If the presence of magnesia be slight and only suspected, a solution of carbonate of ammonia, followed immediately by a solution of potash of soda may be used to test it; if magnesia be in the water it will become milky. Water impregnated with iron is called chalybeate; and it is called sulphurous when impregnated with sulphuretted hydrogen gas.

Pure water is at its greatest density, or heaviest, at 390 of Fahrenheit, that is, at 70 above freezing; if the temperature rises or falls, the water expands.

Salt (sea) water may be rendered fit for washing purposes by adding soda to it. The soda acts by decomposing the chlorides of calcium and magnesium, and by supplying excess of free soda prevents the chloride of sodium from injuring the soap. When it is thrown in the water it will become cloudy, and a white precipitate will be thrown down. When it has settled the water may be poured off for use.

Fermentation is a change effected in the elements of a body composed of carbon, oxygen, and hydrogen without nitrogen. This change produces alcohol and carbonic acid, and if the process be continued the alcohol will be changed into acetic acid or vinegar. Alcohol is, we all know, spirit: the carbonic acid produced by fermentation causes beer or ale to be brisk and sparkling; if suffered to escape by the cask being left open too long, the malt liquor becomesplat, as it is called.

Without fermentation we can have no wine nor beer; yeast, the foam of beer, or of some similar liquor, is produced by fermentation, and consists of a substance called gluten, undergoing putrefaction, in which condition it possesses the property of exciting fermentation. It is the presence of nitrogen in it which gives yeast the power of causing fermentation, which cannot take place unless the gluten is in a putrefying state.

Yeast is put into the infusion of malt called sweetwort, to make it into beer, because the presence of a putrefying body, containing nitrogen, is required to convert sugar into alcohol, and by it the sugar of the wort is changed into alcohol and carbonic acid, and the gluten (of which sweetwort contains a great deal) is changed into yeast.

Grape-juice contains a sufficient quantity of a nitrogenized substance, like yeast, to produce fermentation without any external assistance.

Fermentation in bread is produced generally by yeast, and makes the dough rise, from the carbonic acid gas which is evolved by it. The sticky texture of the " sponge" will not let this gas escape, and it forces up little bladders all over the dough. Heat increases fermentation and expands these gas bubbles, in consequence of which the dough becomes more porous and lighter. For this cause the cook places her dough before the fire to rise; if the dough were to be removed and get cold the air bubbles would condense, the paste would fall, and the bread would be heavy.

Putrefaction is a change effected in the elements of a body composed of carbon, oxygen, hydrogen, and nitrogen.

At the freezing-point of water all putrefaction ceases, and also at the boiling-point.

Perfectly dry substances never putrefy,

Putrefaction cannot take place if there is no air, Air contains the germs of low forms of organic life. Substances can neither putrefy nor ferment without these infusoria being present.

When meat becomes tainted and putrefaction has commenced, it can be stayed and the taint removed by washing it with pyroligneous acid, by covering it for a few hours with powdered charcoal, or by putting a few lumps of charcoal into the water in which it is boiled. Both these substances combine with the putrescent particles and neutralize their offensive taste and smell.

Meat should never be exposed to the action of moonlight, for on a clear moonlight night it will radiate heat freely and grow wet with dew, which causes rapid putrefaction.