It instpntly strikes a black with solutions of iron. Hence a decoction of nut galls is used as a test for iron.
paralus in a fire place, so that if any escape they may go up the chimney.
The receiver must be kept cold, and protected from the light by surrounding it with a wet cloth.
As this acid is decomposed by light and warmth, it must be kept in a cool and dark place. Even these precautions do not prevent its decomposition for more than two or*three months.
Obs. The young pupil may not understand every part of the above process without some explanation.
In the prussian blue, the prussic acid exists in combination with iron. The red oxide of mercury having a stronger affinity for the acid than the iron has, the prussian blue is decomposed, and a prussiate of mercury is formed which is soluble in water. On the addition of the iron filings and sulphuric acid to this solution, the iron absorbs the oxygen from the mercury, which is then precipitated in its metallic state; and at the same instant that the iron is oxidized, it is dissolved by the sulphuric acid. Thus then the prussic acid is set free, because it does not unite with metals, but only with their oxides, and as the iron deprives the prussiate of mercury of its oxygen, the prussic acid remains detached in the solution of sulphate of iron. Now the prussic acid being volatile, while the sulphate of iron is not,it is easy to obtain it by distillation.
423. Prussic acid is a colourless fluid, like water. It has a strong smell resembling peach blossoms, or bitter almonds ; this is so strong as sometimes to excite coughing. Some persons feel a slight stricture across the chest, or pain in the head on breathing it. Animals placed in its vapour, die in a few minutes. When given in large quantities it produces death in two or three minutes. It is indeed the most prompt and active of all poisons. It soon loses these properties on being exposed to the open air, the light also decomposes it in a short time.
Caution. The pupil, on account of the complicated process, and the poisonous qualities of this acid, had better not attempt to make it, until he has considerable knowledge of practical chemistry.
Qbs. This acid is used in doses of a few drops as a medicine, in diseases of the lungs, indigestion, &c.
424. Sebaoic acid, may be obtained from various species of animal fat.
Illus. To hog's lard, melted in an iron kettle add pulverized quicklime, and stir the mixture for a few minutes, raising the heat toward? the end of the process. When the lard is cold, pour on it a large quantity of water; hoil them together and filter the liquor. A brown acid salt will separate on cooling, consisting of lime united with the sebacic acid. The acid is obtained in a separate state by mixing this salt with a sulphuric acid in a retort and distilling. The acid in question ris<;s if the form of a white hquid, which has a penetrating smell, and reddens vegetable blues.
QUESTIONS ON THE ACIDS.
Define what is meant by the term Aero.
Wi.h what substances do the Acids combine to form Salts ?
Are all the acids sour ?
How are the acids formed ?
What substances are called Acidifiable Bases ?
What is said of the combination of Bases with several Do
SES of OXVGEN ?
What Acids are formed by the union of Sulphur with oxygen ?
From what are the Peculiar Properties of the acids and their Names derived ?
How do you know by the Name of an Acid, what proportion* of Oxygen it contains ?
When a base has combined with its Full Proportion of oxygen, how does the Name of the acid End ?
How does the Name of the acid End when the base has combined with only One proportion of oxygen?
Mention* an instance where a base forms an Oxide with the First proportion of oxygen and an Acid with the Second.
Is every acid capable of uniting with each of the alkalies, earths, and metallic oxides ?
How many distinct ingredients does a salt contain ?
What would be the Name of a Salt composed of sulphuric acid and potash ?
Do the acids ending in ous and those ending in ic form similar salts with the same base ?
How do the names of Vie salts end, which are formed with an acid ending in ous ?
How do they end whenformed of an acid ending in ic ?
When the Acid predominates in the composition of a Salt, how is this denoted ?
When the Base predominates, how is it known ?
What is the composition of Nitrate of Potash ?
What would be the name of a salt composed of Muriatic Acid and Ammonia ?
Into how many Classes do the acids admit of being divided?
What is the Acidifying; principle among all the acids ?
MINERAL ACIDS.