MECHLOIC ACID. 



JCECONIC ACID. 



principle to all the mechanical powers wa* long an unsolved problem, 

 and Uif solution may be said to have been firat made known to the 

 world by the discovery of Stovinus, relating to the sustaining power 

 on an inclined plane. A second general principle may be conceived to 

 be that of the comvotition of motion* or form ; and iu discovery is to 

 be ascribed to Galileo. Daniel Bernoulli (about 1726) was the first to 

 demonstrate the rule of the cumpotiiioit of forca independently .-i 

 motion ; but the application of the principle as a means of obtaining 

 general equations of equilibrium seems to have been first made in the 

 Projet d'une Nouvelle Mecanique,' which was published by Voriguon 

 in 1687. 



La Grange treats as a third principle in meclmnics th.it of rirtnal 

 nloritiet. Ky this is meant those which bodies in equUibrio would 

 have at the first instant of their motion, in the event of the equilibrium 

 being disturbed. Indications of this principle are found in the 

 writings of Galileo, Wallis, and Descartes, but John Bernoulli is 

 thought to have been the first who showed its utility in resolving 

 statical problems. [VIRTUAL VELOCITIES.] A general method of 

 solving mechanical propositions was discovered by D'Alembert, and it 

 may be thus enunciated. If there be impressed on bodies motions 

 which they are forced to change in consequence of their mutual actions, 

 thoen motions may be considered as compounded of the motions which 

 the bodies do really take, and of those which are destroyed. Whence 

 it results that these last must be such that if they alone existed the 

 bodies would be in equilibrio. In order to avoid the decompositions 

 of motions which this principle requires, an equation is frequently 

 made between the general analytical expression for a force and the 

 expression for those forces which produce the observed motions. 

 [FORCES, IMPRESSED.] The manner of estimating the value of a 

 mechanical force is various ; and a difference in the expression of the 

 value gave rise to disputes which continued during nearly all the first 

 half of the 18th century. [FORCE.] 



Beside* the principles above mentioned there occur in mechanical 

 investigations several others, which it will be proper to state briefly in 

 this place. 



That which is called the prtierration of liring forces is a consequence 

 of the discovery of Huyghens concerning the movement of the centre 

 of gravity in a compound body. For the space described by that 

 centre is expressed by the quotient arising from the sum of the pro- 

 ducts of the mass of each body into the distance it passes over, divided 

 by the sum of the m ; and since the spaces descended by bodies 

 when acted on by gravity are proportional to the squares of the 

 velocities, it follows that the sum of the products of the mass of each 

 body into the square of its velocity is constant, whether the 'bodies 

 move jointly in any manner, or whether they descend freely through 

 equal vertical spaces. 



Ihe praenration of tlie centre of gravity is a principle which contains 

 the discovery of Newton, that the motion of the common centre of 

 gravity of several bodies is not affected by the mutual attractions of the 

 bodies. It was subsequently extended by D'Alembert, who shows 

 that if the bodies are solicited by a constant accelerative force in direc- 

 tions either parallel to each other or tending to a fixed point, the 

 centre of gravity must describe the same line as if the bodies were 



!': . 



The praerratioa of area* seems to have been discovered simulta- 

 neously by Kuler, Daniel Bernoulli, and the Chevalier D'Arci, about 

 1750. According to the Utter it is an extension of Newton's theorem 

 that the radii rectorei of revolving bodies describe equal areas in 

 equal times, and it consists in this : that the sum of the products of 

 the msssMi of revolving bodies into the areas described by their radii 

 fedora about a fixed point is proportional to the time. Or the sum of 

 the products of the masses into the velocities and into the perpendicu- 

 lars let fall from the fixed point on the lines of direction of the motions 

 is constant. 



The principle of leatt action originally signified, that when bodies 

 act on each other, the sum of the product* of the masses into the 

 velocities and spaces described is a minimum. But considered hi the 

 most general sense, agreeably to the extension given to it by La Grange, 

 the principle consuls in this : that in trajectories described by bodies 

 subject to central forces, the integral of the velocity multiplied by the 

 element of the orbit is always a maximum or a minimum. 



A general outline of that part of mechanics which relates to the 

 equilibrium of solid bodies is given under the word STATICS ; and the 

 details of the subjects may be seen under LEVI.II, Win KI.S, &c. The 

 part of mechanics which relates to bodies in motion appears under the 

 words referred to in the article DYNAMICS. 



M KCHLO1C ACID. This acid was formed in 1885 by Couerbe, by 

 pawing chlorine gas over fused meconin. When purified by solution 

 in |>oUsb, and precipitation by nitric acid, it exists in the state of 

 colourless prismatic crystals, soluble in cold water, but more so in 

 hot : alcohol and ether dissolve it sparingly. It melts at about 257 ; 

 at 876* it is volatilised; and by a strong heat it is decomposed. It 

 contains 



Hydrogen 4-07 



Carbon 4872 



47-21 



lOO'OO 



MECONAMIC ACID. [MECOSic AUK] 



M I'.t 'i iN ATKS. [MECOSIC ACID.] 



MECONIC ACID (C U HO,,,3UO). A substance found in opium, 

 in which it exists in combination with the alkali morphia. It was first 

 noticed by Seguin in 1804, and a few yean after, more particularly 

 described by Sertuerner, who named it aucun (/ifcuv), poppy. Meconate 

 of linn- is one of the results of a peculiar process for obtaining morphia 

 from opium [Orirx, ALKALOIDS OF] ; this is put into ten times iu 

 weight of water at 200*, and hydrochloric acid is added until it in 

 dissolved ; the solution is to be filtered, and on cooling it deposits 

 bi-meconate of lime in the [state of light, scaly, or acicular crystals ; 

 these are again to be dissolved in hot am) very dilute hydrochlor: 

 which separates the remainder of the lime, and on cooling, the meoonic 

 acid crystallises in scales containing six equivalents of water of crystal- 

 lisation. They are to be freed from colouring matter by subsequent 

 treatment with purified animal charcoal, and recrystallisation. Jl 

 acid has then the following properties : it acts on litmus paper, and has 

 a sour taste ; it is soluble in four times its weight of water, and also in 

 alcohol. The crystals do not alter by exposure to the air, but when 

 heated to 212 they lose 21 '5 per cent, of water, and become opaque. 

 Although when heated even to near 250 the acid is not totally decom- 

 posed, yet the boiling solution gives out carbonic acid gas, and a brown 

 substance is formed, which is comenic acid. When strongly heated, it 

 is totally vaporised. When mixed with n solution of chloride of gold, 

 and heated, it is decomposed, and metallic gold is precipitated. ThU 

 acid possesses the characteristic property of forming a purplish-red 

 coloured solution with the penults of iron, and this is regarded as one 

 of the best tests of its presence in the opium from which it is derived. 

 It has been asserted that meconic acid is on antidote in cases of 

 poisoning by corrosive sublimate, but this is not the case. It has no 

 effect whatever. 



Meconic acid is tribasic ; one, two, or three atoms of the water in the 

 above formula being replaceable by on equal number of equivalents of 

 a base with formation of mono-, bi-, or tri-metallic salts, 

 meconatet. Then- properties are as follow: Meconate of Ammonia 

 crystallises in quadrilateral prisms, dissolves iu one and a half times its 

 weight of water, yields water when heated, and afterwards sublimes 

 without decomposing. Meconate of Potash crystallises in tables and 

 leaves, contains water of crystallisation, and is soluble in twice its 

 weight of cold water. Meconate of Soda crystallises in fine needles, 

 which contain much water of crystallisation, and are soluble in five 

 times their weight of water. Meconate of Lime forms acicular crystals, 

 which contain water of crystallisation, and are soluble in eight times 

 their weight of water. When the acid is in excess the salt crystallises 

 in prisms, and is difficultly soluble in water. Meconate of Maynetia 

 when neutral is only slightly soluble, but the supersolt dissolves readily ; 

 it crystallises in flattened needles, which are brilliant and transparent, 

 and have an acid and bitter taste. Meconate of jiaryta is slightly 

 soluble iu water. Meconate of Iron is a colourless and very soluble 

 salt, which becomes red by exposure to the air, and more rapidly by 

 the addition of nitric acid. The Permeconate of Iron is also a soluble 

 salt, and is of a fine red colour, destroyed by heat, by sulphuron 

 and protoxide of tin. Meconate of Silver explodes when heated. 

 Meconate of Oxide of Ethyl, or Meconic Ether, or Ethiil-mcconic acid 

 (C,H S 0, 2HO, Cj.HO,,), separates out iu acicular crystals on evaporating 

 the liquid formed on passing dry hydrochloric acid gas through a 

 solution of meconic acid in absolute alcohol. It forms very stable 

 salts, called Ethylmefonatet. The mother-liquor from the preparation 

 of ethylmcconic acid contains crystalline Diethylmcconic acid (2C.H.O, 

 HO, C..HO,,). 



If economic acid (C 14 H,NO,,) is precipitated when hydrochloric acid 

 is added to Mcconamatc of A mmonia. The latter salt is produced by 

 the reaction of ammonia and ethylmcconic acid. 



Comenic acid, Metameconic acid, Parameconic afid (C,.H 2 0,,2HO). 

 It has been mentioned above that when a solution of meconic at -i I is 

 heated to ebullition, carbonic acid is evolved, and a brownish solution 

 results ; this consists of colouring matter and comenic acid. When a 

 meconate, as of potash or lime, is boiled with hydrochloric acid, no 

 colouring matter results, and yet comonic acid is form. 'I. 



This acid is soluble in sixteen times its weight of boiling water, and 

 separates on cooling in hard anhydrous grains, which, like the meconic 

 acid, redden the persalts of iron, but they differ from it in every other 

 respect. 



It is formed by the mere separation of carbonic acid, by subtracting 

 two equivalents of which from meconic acid we obtain the acid in 

 question : 



c,,no M , SHO 2co, = c,,u,o,, :HO 



Meconic acid. 



Comenic acid. 



Comenic acid is bibosic, forming neutral and acid comenate,i. Ktliyl- 

 comenic acid is formed in a similar way to ethylmcconic acid. ( 

 comenic acid (C,,H,C10 10 + 3 Aq.) is obtained by the action of chlorine 

 on comenic acid. It crystallises in short prisms. 



Comrnamic acid (C,,H.NO,). Prepared by the action of heat upon 

 a solution of comenate of ammonia. On adding a little hydrochloric 

 acid, and cooling, it crystallises out in plates. The comcnamatci ar 

 monobasi<< 



