Page:The American Cyclopædia (1879) Volume XI.djvu/128

120 MANNITE to the government of the Baptists," and drew up a plan for such an institution. In 1764 the k-jjNlature granted them a charter, and in 1765 Mr. Manning, then hut 27 years of age, was ap- pointed "president and professor of languages and other branches of learning, with full power to act in these capacities, at Warren or else- where." The college went into operation at Warren in 1766, and on its removal to Provi- dence in 1770, Mr. Manning went with it, and also became pastor of the first Baptist church in that place. During the revolution, when the college edifice was occupied as a military bar- rack, and afterward as a hospital, he was ac- tively engaged in clerical duties, and also ren- dered important services to the patriotic cause. In 1783 ho resumed his duties at the college, and in 1785 he was chosen to represent Rhode Island in congress, but after six months' service resigned. He resigned the presidency of the college in 1790, and his pastorate in April, 1791. (See BROWN UNIVERSITY.) .MA.YMTK, or Mannitose, also called sugar of manna and sugar of mushrooms (CgHuOe), one of the glucoses, which was discovered by Proust, and its composition determined by Lie- big. It exists in a great number of vegetables, and in the saccharine juices which have under- gone viscous or lactic fermentation ; it is gen- erally extracted from manna, by digesting this substance with boiling alcohol, filtering while hot, and crystallizing ; it should be purified by repeated crystallizations. On the transforma- tion of starch into glucose by boiling with dilute sulphuric acid, it is also formed as a secondary product ; and finally Linnemann in 1862 obtained it by the action of nascent hy- drogen on glucose. Mannite is a solid sub- stance, fusible between 160 and 165 C., and when once melted it can remain liquid at 140 C. It exercises no action on polarized light ; it dissolves in 6 times its weight of water at 18 C., and in 80 parts of cold alcohol of the strength of 89 per cent., and much more readi- ly in boiling alcohol. It is not soluble in ether, and absolute alcohol only dissolves 14 per cent. of IN weight of monnite. Mannite crystallizes in anhydrous, thin, colorless, four-sided, silky prisms, which sometimes grow to a consider- able size. It does not ferment except under very unusual conditions ; does not reduce oxide of copper to the state of suboxide, but hinders the precipitation of sulphate of copper by the fixed alkalies, causing the formation of a beau- tiful blue-purple solution instead. In its chem- ical character, mannite is now regarded as a polyatomic (hexatomic) alcohol. Berthelot has shown its close analogy to glycerine, and has obtained a great variety of salts (called man- nitanides) from it by heating mannite with dif- ferent acids to a temperature of between 200 and 250 C. With a mixture of nitric and sul- phuric acids it gives nitro-mannite. The ni- trates of silver and mercury and the chlorides >f silvr and mercury are not reduced by man- nite even at boiling heat ; the acetate and ox- MANOMETER ide of silver, however, if heated with mannite or left in contact with it at ordinary tempera- tures, yields a speculum of silver. Compounds of mannite with barium, calcium, strontium, &c., have been prepared by Ubaldini. In the presence of beer yeast mannite does not fer- ment ; but if its solution be maintained at 40 C., after having been mixed with chalk and poor cheese, pancreatic tissue, or albumen, fer- mentation takes place, hydrogen and carbonic anhydride are disengaged, and alcohol is pro- duced along with lactic and butyric acids. MAN-OF-WAR BIRD. See FRIGATE BIRD. MANOMETER (Gr. fiav6^ rare, and fttrpw, measure measurer of rarity), an instrument employed to measure the pressure exerted by a confined portion of gas or vapor. The force is usually expressed in units of atmospheric pres- sure, called atmospheres, which are equal to 30 inches height of a column of mercury, or nearly 15 Ibs. to the square inch. It will therefore be easily seen that mechanical ingenuity may devise several forms of the instrument. These various forms may be classified under three different general forms, which act upon different prin- ciples: 1, open-air manometer; 2, confined- air manometer ; 3, metallic-spring manometer. An open-air manometer is shown in fig. 1. It consists of a vessel containing mercury in which a vertical tube & dips. The vessel also admits a tube, a, which connects with the boil- er or chamber of compressed gas or steam. Calling Boyle's or Mariotte's law correct for all pressures, if the compressed gas has a density twice as great as it would have at the ordi- nary atmospheric pressure, it will raise the column of mer- cury in the tube 5 30 inches ; if five times as dense, the height of the mercurial col- umn will be 150 inches, cor- responding to 75 Ibs. to the square inch. There may be many forms of open-air ma- nometers, and the modifica- tions are generally for the purpose of increasing the con- venience of the apparatus by shortening the distance of the rise of the mercurial column. The multiple-branch manometer, fig. 2, is a convenient form. An iron tube is bent upon itself, forming several U-shaped flexures, ter- minating in a vertical tube of glass, C D, fur- nished with a graduated scale, and open at the top. Mercury occupies the lower flexures and portions of the tube. When the com- pressed steam or gas is admitted, it presses upon the mercury in the first branch, A, for- cing it down, and therefore up in the second branch. If it forces A down 10 inches, the difference of level in the two branches will be 20 inches. If there are 10 single or 5 double FIG. 1. Mercurial Manometer.