Surprising Tests WITH Household AMMONIA (Jun, 1933)
Surprising Tests WITH Household AMMONIA
Simple Experiments and Home-made Apparatus Extend Your Knowledge and Speed the Work You Can Accomplish in Your Own Laboratory
by Raymond B. Wailes
IT IS surprising what the amateur chemist can do with a fifteen-cent bottle of ordinary household ammonia.
Being a mixture of ammonia dissolved in water, this pungent-smelling liquid offers an ever-ready supply of ammonia gas for the home laboratory. Even at room temperature, the gas is released from the liquid. By heating it, the experimenter can obtain the gas in larger quantities.
Strictly speaking, household ammonia is not ammonia at all, but ammonia water or ammonium hydroxide. Although ammonia can be liquefied, it is a colorless gas at normal temperatures. The fact that it dissolves readily in water makes the manufacture of ammonia water possible.
You hardly would suppose that the fumes rising from an open bottle of house-hold ammonia are inflammable. Yet, ammonia gas can be burned. To demonstrate this, place an ounce or two of household ammonia in a small flask. Fit the mouth of the flask with a cork containing
a metal or glass outlet tube and heat it. Ammonia gas will flow from the outlet tube and a match held close to the tip will cause the gas to burn as long as the match flame is present. If the outlet tube is placed in an atmosphere of oxygen, the ammonia gas will not only flame but will burn steadily. Like hydrogen, ammonia gas is lighter than air. For this reason it can be collected by holding an inverted bottle over the mouth of the generator flask. When the bottle has filled, it can be tipped upright by closing its mouth with a flat card or square of glass.
Collect a bottle of the gas and seal it with a card in this manner. If the bottle is then righted, the card removed, and a burning match dropped in, the gas will flame and glow slightly as it burns.
Household ammonia often contains impurities such as soap and oleic acid that make it unfit for use in experiments requiring pure ammonium hydroxide. The amateur chemist can prepare pure ammonium hydroxide, however, by heating some household ammonia and allowing the gas evolved to bubble through water. Make some, place it in a rubber-stoppered bottle, and label it “ammonium hydroxide.” You’ll find that it will be a useful addition to your stock of chemicals.
It has been found that as many as 700 volumes of ammonia gas can be dissolved in a single volume of water. This particular property forms the basis of an interesting fountain experiment similar to the one described some months ago in connection with sulphur compounds (P.S.M., Sept. ’32, p. 50).
First, select a large-mouthed bottle and fit it with a cork having a hole through its center. Push the glass portion of a straight medicine dropper through this hole so that the tip of the dropper is inside the bottle, and connect a short length of rubber tubing to its outer end. Fill the tube and dropper with water and snap a > pinch clamp over the middle of the tube.
FILL the bottle with ammonia gas by inverting it over a heated flask containing household ammonia and quickly insert the cork containing the dropper. By squeezing the rubber tube above the clamp you can cause some of the water in the tube to flow into the bottle and dissolve some of the gas. This will form a partial vacuum inside the bottle.
Holding the bottle inverted, immerse the lower end of the rubber tube in a beaker or glass of water and remove the pinch clamp. The vacuum in the bottle will suck the water up through the tube and dropper and create a miniature fountain.
You can make the effect more mystifying by placing several drops of phenol-phthalein solution in the water before you open the pinch clamp. The water will remain colorless until it enters the bottle.
As it mixes with the gas, however, it will turn red because of the alkali effect of the ammonium hydroxide formed.
When heated with a caustic, such as lime water or lye water, all ammonium compounds decompose to form ammonia gas. For instance, if sal ammoniac is mixed with powdered lye and water, ammonia gas is evolved without the presence of heat. This, by the way, is a very simple and inexpensive way to prepare ammonia gas in the laboratory. Sal ammoniac can be purchased in any drug store and almost every home has a can of powdered lye on hand. The same type of reaction will take place if the sal ammoniac is mixed with lime water, excepting that in this case heat will be necessary to complete the process.
WITH certain types of ammonium salts and alkalies, you do not even have to add water to produce the ammonia gas. Sodium carbonate (soda ash) and ammonium chloride, both odorless substances, will react to form ammonia gas when they are rubbed in the palms of your hands.
Another simple way to make ammonia gas is to heat certain types of organic matter such as hair or pieces of animal horn. As a laboratory experiment, the amateur chemist can place some finger nail clippings in a test tube and heat them. A small piece of red litmus paper dampened and placed at the mouth of the tube will detect the alkaline trace of the ammonia gas evolved. This experiment can be made more effective by placing a small amount of dry lime or lye in the tube with the nail clippings. Incidentally, when handling lye it is best to use a glass or metal scoop.
Since ammonia and all its compounds contain nitrogen and hydrogen, the gas can be decomposed by the experimenter to obtain nitrogen. This is done by passing the gas over a hot metallic oxide. In the process, the hydrogen in the ammonia combines with the oxygen of the oxide, forming the metal and water, and the free nitrogen gas is released.
In the home laboratory the chemist can perform this experiment with a simple piece of apparatus assembled from various odds and ends.
SOME copper fly screening is first made into a small roll about eight inches long and placed in a short length of iron gas pipe. The outlet tube from an ammonia gas generator is led into one end of the pipe through a tight-fitting cork while a long outlet tube having a flexible rubber joint is fitted through a cork in the other end.
The entire apparatus should be arranged high enough to permit the iron pipe and the generator flask to be heated. The flask can be placed on an improvised
stand made from short lengths of ten-cent curtain rods. The rods should be bent at the proper points and threaded or glued into holes in a small wooden base. A square of iron fly screening placed over the uprights will support the flask. With the ammonia generator disconnected, heat the iron pipe with a gas burner. This will cause the copper screening to become oxidized, forming a coating of copper oxide. Then connect the generator, apply heat, and immerse the end of the outlet tube leading from the other end of the iron pipe in the water-filled collecting trough.
THE trough can be made from a ten- cent baking tin by soldering a bridgelike strip of tin across one end at such a height that it will be below the level of the water. Fill an empty bottle with water and carefully place it inverted on the bridge directly over an inch hole cut in the metal.
When the generator flask is heated, ammonia gas will be released and will flow over the heated copper oxide in the iron pipe. The hydrogen is removed from the ammonia by the hot oxide and the pure nitrogen gas bubbles from the outlet tube.
To collect the gas, place the outlet tube under the hole in the metal bridge supporting the bottle in the trough. The gas will bubble up into the bottle and displace the water. When the bottle is completely filled with the gas, carefully slip a piece of glass under the mouth and remove it from the trough.
By experimeriting with the nitrogen you collect, you will find that it is a very inactive gas. The fact that you can collect it over water shows that it is not particularly soluble. Carefully raise a glowing splinter of wood into an inverted bottle of the gas and you will find that the ember is extinguished. Nitrogen gas neither burns nor supports combustion. Further tests will show the gas to be tasteless and odorless.
In fact, nitrogen does not combine readily with many substances and its compounds are easily decomposed. The ease and violence with which most of its compounds break down are well illustrated by two common nitrogen-containing substancesâ€”nitroglycerine and gun cotton.
Ammonia and ammonium salts offer many other interesting and instructive experiments to the home chemist. The hydroxides of many metals, for example, can be formed by adding ammonia water (household ammonia will do) to solutions of the metals. Such solutions as copper sulphate, lead nitrate, iron chloride, iron sulphate, nickel sulphate, cobalt compounds, alum, and magnesim sulphate (Epsom salts) lend themselves well to this experiment.
The hydroxides form as curdy, jelly-like precipitates. In some cases they are so thick that the test tube in which they are made can be inverted without spilling the contents.
In these experiments, it is interesting to note that the precipitates of copper, nickel, and cadmium hydroxides will dissolve when more of the ammonium hydroxide is added to the solution. In the case of the copper sulphate, the resulting liquid will take on a deep azure blue color. If very strong ammonium hydroxide is used in the precipitating and dissolving processes, the blue solution will dissolve tiny bits of paper. This particular property has been used in the manufacture of artificial silk.
By adding water to a mixture of ammonium nitrate and zinc dust the experimenter can produce a small spontaneous flame. As the water is added, the mixture will bubble and smoke until it finally burns. Care must be taken, however, not to add too much water.
AS A safeguard, the mixture can be placed on the tin cap from a preserve jar and newspaper can be spread on the laboratory table to catch the chemicals should the mixture spatter.
No discussion of ammonia gas would be complete without some mention of its commercial uses. The most important uses of ammonia are as a refrigerating agent and for the preparation of ammonia water. Large quantities of ammonia, however, are also used in the manufacture of sodium carbonate, ammonium salts, and nitric acid.