lowing 10 gallons of water per person per day, the soap used in softening hard water for a family of five would amount to over 21 pounds per year for each degree of hardness. Many hard waters have 10 to 20 degrees of hardness. It is therefore obvious that the waste may amount to something quite serious.

A hundred gallons of hard water can be softened by the use of about two thirds of an ounce of washing soda crystals for each degree of hardness. Water for a family of five persons estimated as above (50 X 365 = 18,250 gallons) could be softened by the use of 71⁄2 pounds of soda per annum, for each degree of hardness. The 7 pounds of soda would cost about

one ninth as much as the 21 pounds of soap.

With a water of a hardness of 10 degrees the comparison would be between 210 pounds of soap and 75 pounds of soda. Adopting the wholesale prices of 6 cents per pound for soap and 2 cents per pound for soda, we have:

Cost of softening with soap, 210 pounds at 6 cents
Cost of softening with soda, 75 pounds at 2 cents

Saving when soda is used

$12.60

1.50

II.IO

In softening water with soda, the use of too much soda. should be avoided. What is not used up in the reaction with the calcium compounds is left in the water. If a great excess is used, the water may be rendered so strongly alkaline as to injure delicate fabrics.

CHAPTER XXIII

AMMONIA AND THE AMMONIUM RADICLE

Experiment 72.

Materials:

Red litmus paper.

Turmeric paper.

Pour a little ammonia water into a test tube. Note the odor and the effect produced on pieces of red litmus paper and yellow turmeric paper held at the mouth of the tube. Bring an open bottle of concentrated hydrochloric acid near the mouth of the test tube. What forms?

Experiment 73.

Materials:

Solid specimens of:

Ammonium carbonate.

Ammonium chloride.

Ammonium nitrate.

Ammonium oxalate.

Ammonium sulphate.

Note whether these salts have the odor of ammonia. Is there an exception among them? Of the others, mix one with slaked lime and heat gently, heat one with sodium hydroxide solution, and one with potassium hydroxide solution. Note odor in each experiment.

Ammonia is the name of the gas of pungent odor which escapes from ammonia water (aqua ammonia, liquor ammonia). Ammonia gas is formed in nature in the putrefactive decomposition of animal and vegetable matter containing nitrogen. The odor is often distinctly perceptible in horse stables in which manure has been allowed to accumulate.

Ammonia was formerly obtained, for medicinal use, by destructive distillation of nitrogenous animal wastes, such

as bones, hoofs, and horns; hence the name, "spirit of hartshorn," sometimes applied to aqua ammoniæ. The compound is now manufactured as a by-product of the coal-gas industry. In the process of destructive distillation (heating the coal in closed retorts) much of the nitrogen of the coal escapes with the gas as ammonia, which is afterwards separated from the other constituents of coal gas and obtained pure. (See Chapter XII.)

The gas can be converted into a liquid by cold and pressure, and in this form is used in the refrigerating machines of cold-storage plants and ice factories. This anhydrous

FIG. 37.

Experiment 74. Appa

ratus for generating ammonia.

liquid ammonia is not to be confounded with the more commonly used liquor ammoniathe solution of this gas in water. Ammonia contains the elements nitrogen and hydrogen and has the formula NH3.

Experiment 74.*

Materials:

Ammonium chloride.

Slaked lime.

Red litmus solution.

Apparatus:

Figure 37. Small

round

bottomed flask connected through drying tube containing quicklime to upward delivery tube.

Figure 38. Fountain apparatus, consisting of (a)-liter round-bottomed flask, fitted with tightly fitting twoholed stopper, carrying (1)

a glass tube reaching nearly to bottom of flask, (2) a medicine dropper; (b) a retort stand with ring to hold this flask in inverted position; (c) glass dish or beaker.

Mix ammonium chloride and slaked lime and heat gently in the generating flask in the hood, collecting the gas in the flask of the fountain apparatus.

Fill the medicine dropper with water, and the glass dish with the red litmus solution. From time to time hold an open bottle of concentrated hydrochloric acid near the mouth of the inverted flask, and when a heavy cloud of white fumes is observed, insert the rubber stopper and transfer the flask to its position in the retort stand of the fountain apparatus. Press the bulb of the medicine dropper so as to force a few drops of water into the apparatus. These few drops dissolve practically all the ammonia in the flask, thus creating a vacuum, into which the water is then forced by the pressure of the air on the water in the dish. Note also the effect of the ammonia on the litmus. What does this indicate?

Ammonia gas is enormously soluble in water. One gallon of water

will absorb about 700

gallons of ammonia, or FIG. 38.—Experiment 74. Fountain apparatus. about one half its own

weight of the gas. Thus about one third of the weight of the strongest ammonia water consists of the gas, and the

K

Com

water constitutes the other two thirds. For ordinary household use much weaker solutions than this are sold. mercial "household ammonia" sometimes contains impurities which fade colors or cause white materials to turn yellow. It will be found safer and more economical to buy concentrated ammonia from a druggist, dilute it with its own volume of water, and keep it in bottles carefully closed with glass or rubber stoppers. This solution can be further diluted with three times its own volume of water for most household uses. In pouring ammonia water from bottle to bottle discomfort can be avoided by holding the bottles above the level of the eyes. The escaping gas, being lighter than air, ascends.

The Ammonium Radicle

Ammonia water has an alkaline reaction, and, like the hydroxides of metals, neutralizes acids, producing salts. These facts lead us to infer that when ammonia gas dissolves in water, it combines with the water, forming a hydroxide.

Ammonia + Water
NH3 + H2O

=

Ammonium hydroxide

=

NHOH

The base would thus be the hydroxide of a radicle, NH, made up of nitrogen and hydrogen. To this radicle the name ammonium" is applied. The same radicle is present in all ammonium salts, e.g. ammonium chloride (sal ammoniac) NHCl, ammonium sulphate (NH4)2SO4, and ammonium carbonate (smelling salts) (NH4)2CO3. In their solubilities the ammonium salts are very similar to the corresponding salts of potassium.

To include ammonium hydroxide among the bases we may expand our definition of a base (see p. 94) into the following:

A base is the hydroxide of a metal or of a radicle which plays the part of a metal.