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ACIDS (acida); a class of compound bodies, which have the following characteristic properties: the greater part ot them, a sour taste, and most of them are very corrosive; they change the vegetable blues to red, are soluble in water, and have great affinity for the alkaline, earthy, and metallic oxyds, with which they form neutral salts. Some acids have no sour taste, but their affinity for the three classes of bodies abovementioned is always characteristic. If a few drops of sulphuric acid, nitric acid, or muriatic acid, be added to a solution of blue becomes reel. ine same is tne case it they be ad ied to other vegetable colors, as violet, &c. Hence these colors are employed as tests of acids, that is, to ascertain when they exist in any substance. We may add the infusion to the fluid in which we are trying to detect an acid, but a more convenient method is, to spread it on paper, and allow it to dry. If a strip of this be put into a fluid in which there is an acid, it instantly becomes red. Some acids appear only in a fluid state, either gaseous, as carbonic acid, or liquid, as sulphuric acid ; others appear in a solid form, or crystallized, as benzoic acid, boracic acid, &c. All acids are compound bodies, and are sometimes divided into four classes, the three first of which are compounded with oxygen ; the fourth class consists of those which, at least according to some modern chemists, have no oxygen; e. g. sulphuretted hydrogen. The first class consists of acids compounded with oxygen and one other body; the second class comprises the acids compounded of carbon, hydrogen and oxygen; the third class consists of those acids which contain nitrogen, in addition to the three substances abovementioned. The ancient chemists were acquainted with but few of the acids now known; tlrey divided them, according to the .kingdoms* of nature, into mineral, vegetable and' animal acids. This division, however, cannot now be retained, as there are some acids which appear in all the kingdoms; e. g. phosphoric acid. If the same radical be compounded with different proportions of the acidifying principle, forming different acids, the^most powerful acid receives a name from the radical, terminating in ic; the weaker, a name formed in the same manner in ous; e. g. sulphurous acid and sulphuric acid, nitrous and nitric acid; and, where there are intermediate compounds, the term hypo is occasionally added to the compound next above it in point of acidity. Thus hyposidphuric acid signifies an intermediate acid between sulphurous and sulphuric acids; hypophosphorous acid, an acid containing less oxygen than the phosphorous acid. {For Prussic acid, Pyroligneous acid, &c. see Prussic, Pyrolignioitf, <&c.) _¦o¦o Acras ; hurricanes of snow which prevail among the Cevennes, in the south of France. Villages are sometimes so rapdly covered, that the inhabitants have no means of communication, but by cutting passages under the snow. ACKERMANN, Rudolph, was born in 1/04, at senneeoerg, in saxony, wnere his father was a saddler. He received his education at the Latin school of his native city, and, after learning the trade of 'lis father, travelled through the country as a journeyman, according to the custom of Germany. After residing for some time at Paris and Brussels, he went to London. He there became acquainted with Facius, a German, who had undertaken to conduct a journal of fashions, (Journaldes Modes,) and met with tolerable success. A. soon afterwards published, in the same way, drawings of coaches and curricles, invented, drawn and painted by himself. The novelty and elegance of the forms excited universal attention, and he received orders for drawings from all quarters. This laid the foundation of a trade in works of art, which his activity, attention and precision in business so much enlarged in a short time, that he was enabled to marry an English woman, became a citizen of London, and founded an establishment called Repository of Arts, in the Strand, in the centre of London. It is one of the curiosities of the British capital, and gives employment to "several hundred men. An account of every thing new has appeared for 8 years in A.'§( splendid journal, Repository of Arts, \tdterature and Fashion, the first series of which, in 14 volumes, costs £18; and the new series already amounts to more than 40 numbers. Every number contains three or four elegant, colored copperplates. For 8 years he has also been engaged in a series of topographical works, exhibiting all the splendor of British aquatinta, which already constitute a small library, and, for truth of design and elegance of execution, are hardly surpassed by any similar undertaking in any country. He now has the most instructive books of the English and other languages translated into Spanish, (principally by the wTellknown Blanco White,) and sends them to America, where his eldest son is engaged, in Mexico, in extensive dealings in books and works of art. For some years he has also published the first souvenir in England, called the Forget me not When the association was formed, in 1813, for the relief of those who had been plunged into misery by the war in Germany, A. showed himself an active philanthropist. A. is now the best lithographer in London. He employs in the summer 600 men, every day, in and around London.