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merely to rupture the membranes ; an ope-ration, than which none in midwifery ismore easy, and in this way discharging thefluid of the ovum, you more or less com-pletely arrest the discharge. The operationis beautiful-simple, as it is effectual.The placenta not lying over the os uteri,

it now and then happens, that, notwithstand-ing the discharge of the liquor amnii, theflooding still continues. Now, in cases ofthis kind, provided the patient’s life appearto be in danger, the only remaining resourceis, to bring away the child by the operationof turning ; for of the remaining means forarresting the bleeding, the most powerfulis the thorough evacuation of the uterus.

If the softer parts are rigid, if the os uteriis shut and unyielding, if the patient is in astate approaching to asphyxia, so that it is necessary to wait till she rally, you must refrain from interfering ; remain in thehouse-abide in the bed-chamber ; be pa-tient-be vigilant ; and when your patienthas rallied somewhat, make an examination.to know whether the hand can yet be intro-duced with safety; and if from the laxity ofthe softer parts, and the dilatation of theuterine mouth, it seem evident that turn-

ing may be safely executed, let the handwithout delay be carried into the cavity ofthe uterus, for the sooner the fœtus is ab-stracted the better,The following are the principal errors

which you are apt to commit in the ma-nagement of those floodings in which the placenta is not lying over the mouth of theuterus, and they well deserve a little consi-deration. The neglecting to ascertain whe-ther the placenta is, or not, lying over themouth of the womb, is a capital fault, foryour whole practice must turn upon thatknowledge ; if the placenta is lying over themouth of the womb, one kind of practicebecomes ’proper; if it is not so situated,another. The trusting too much to medici-nal treatment, to the exclusion of manualinterference, is another great error in themanagement of the latter floodings. In the

general, as I have observed on precedingoccasions, the best accoucheurs are thosewho interfere the least with the fingers orhand ; but if there be an exception to thatrule, that exception lies in the managementof these flooding cases of the latter months,where, owing to the danger arising fromthe large discharges of blood, practicesprompt and efficacious are peremptorily re-quired. Denman, a cautious and experi-enced practitioner, remarks, I think, some-where, that if we are to err in those cases,we ought rather to err on the side of prompti-tude than procrastination; adding, if I re-member right, that it is rather a sign ofwisdom than of officiousness, to show areadiness in these cases to discharge the

liquor, or to deliver by the hand. Again :if you have not seen much of flooding cases,you are liable to be alarmed at the quantityof blood that is discharged, being induced,of consequence, to carry your hand into theuterus, when, perhaps, it would base beena better practice to have confided the sup-pression of the bleeding to the rupture ofthe membranes, an operation at once saferand more easy. Further, the delivery of pa-tients in a hurry is a great error ; it is morethan an error, it is a crime. Into this crime,in unguarded hour, you may be seduced, ifyou have delayed too long the delivery,when really required; anxious to save yourreputation and your patient, you accelerate,you bruise, you tear, you destroy. I nowrepeat what 1 observed once before : in ob-stetrics, a thrust of the hand into the uterusmay prove as fatal, and will generally pro-duce a more extensive wound, than thethrust of a bayonet. The waiting for painsis an error which you may commit; onthis I dwelt in a preceding lecture. Youhave not Iorgotten the silly rule ; wherethere are large floodings, the womb may beparalysed; nor should you, therefore, if

symptoms require it, he deterred frommanual interference, merely because the

pains are wanting. The absence of pains,if it proves anything, rather proves the ne-cessity of obstetric assistance, because it

proves that the natural efforts are inade-

quate to the expulsion of the fœtus.

LECTURES ON CHEMISTRY,BY

PROFESSOR BRANDE.

Delivered at the Royal Institution of GreatBritain.

LECTURE XXX.

On the Ckloride, Nitrate, Sulphate, Phosphate,and Carbonate of Lime.

AT the conclusion of the former lecture,I briefly explained the formation of thechloride of calcium, which, I stated, was pro.duced by heating lime with chlorine, bywhich process its oxygen is evolved, andthe chlorine unites with the metallic base ofthe lime, (calcium,) to form chloride of cal.cium, and I gave you my reasons for con.

sidering this compound as distinct frommuriate of lime.

Chloride of Lime, or, Oxymuriate of Lime.-Now, if lime be exposed to chlorine at acommon temperature, the chlorine is ab.sorbed as in the former case, but no oxygenis given out, so that, in fact, you have a truechloride of the earth lime, and not a chlo-

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ride of calcium. Chlorine is, as you are

aware, a very powerful bleaching agent;but, as a gas, it is very inconvenient for

transportation, and difficult in its applica-tion ; but here the chlorine is held in com-bination with the lime, and the affinity bywhich it is held is so slight, that it has the

power of acting upon vegetable colours as ifentirely free. So weak is the affinity bywhich it is united to the lime, that by mereexposure to the carbonic acid gas of the

atmosphere the chlorine is evolved, andacts as a very powerful bleaching agent.When water is added to the chloride oflime, it effects its partial decomposition ;one half of the chlorine leaves the lime, anddissolves in the water ; and this is the

bleaching liquid of the shops, which is soldat a high rate, although it cannot cost morethan a farthing a gallon. Sometimes thisfluid is applied immediately to the sub-stance to be bleached, but sometimes a weakacid is added to destrov the slight affinityof the chlorine for the lime, and vou willsee.by this addition, how much the bleach-ing power of the fluid is increased. The

manufactory of the chloride of lime is car-

ried on on a large scale in the north of Eng-land, by passing chlorine into leaden cham-bers containing hydrate of lime in fine

powder. So weak is the affinity which existsbetween the lime and the chlorine, that, inthe vessels used by the bleachers, car-bonate of lime is generally precipitated. ’

The chlorate of lime is a salt of very littleimportance ; it is very soluble in water,verv deliauescent. and of a sharp bitterishtaste. It is easily produced by dissolvingcarbonate of lime in chloric acid. Oxygenis evolved when it is exposed to heat, andthe salt is then reduced to a chloride.

. The nitrate of time is constituted of nitricacid and lime ; it is verv soluble in water,dissolving in less than half its weight ofwater; and, by the addition of a solution ofcarbonate of potash to the solution of thecitrate of lime, a sufficient quantity of thecarbonate of lime is thrown down to makethe whole a solid; and this was called bythe alchymists a chemical miracle. It issometimes found in old plaster and mortar,from the washings of which, by the additionof carbonate of potash, nitre is procured;and I have already spoken of the productionof this salt in the artificial nitre-beds.Then there are the sulphuret, the s2ilphite,

and the hyposulphite of hme ; but I do notenter into detail of the properties of thesesalts, because they are of little interest. Inthe second number of the Edinburgh Journalof Science, edited by Dr. Brewster, there isa very good paper by Mr. Herschel on thesesubjects, to whom we are indebted for ourcorrect knowledge of these salts.The sulphate of time is a compound of great

importance in its application in the arts ; itis composed, in its dry state, of one pro-portional of lime 28, and one of sulphuricacid 40, forming 68 as its equivalent num-her. In the crystalline form, the state inwhich it commonly occurs in nature, it con-tair.s two proportionals of water, which itwill be necessary to remen-ibe-c, in consider-

ing the action of heat upon this salt. Now,when you heat the crystallised salt, youdrive off a quantity of the water of crys-tallisation, and it becomes opaque and pulve-rulent ; and, in this state, it is known as

the plaster of Paris. If you again mix thiswith water into the consistence of cream,it sets, as it is called, into a hard mass, andis employed in taking casts, and in themanufacture of certain cements, as theRoman cement, and so forth. It dissolves

sparingly in water ; one part requiring 350

parts of water for the solution of the

crystallised salt. It imparts to the water abitter taste ; and you tind that it renders

water very hard ; so that if you endeavour towash your hands in water containing anynotable quantity of the salt, the soap ad-heres to the hands, and a very disagreeablecompound is produced, which sticks to the

skin ; this is owing to the decomposition ofthe soap by the lime. When I sav that it

renders water hard, I am only speaking ge.nerally of the water in and about London;all the superficial springs in and about Lon-don afford water of this kind, good enouglito drink, but not well fitted for washing. Ifyou go deeper, you come to very pure water,containing scarcely any lime, but a little car-bonated alkali. The tests of this substanceare of course those which indicate the pre-sence of’ sulphuric acid and lime, and al-

though it may be rather premature to gointo this subject at present, I shall showyou the manner of operating on water whichyou suspect to contain sulphate of’ lime,with one or two of these tests. If we adda little muriate of baryta to the water, weshall get an indication of the presence ofsulphuric acid by the precipitation of a densewhite insoluble powder, which is the sul-phate of baryta. Then there is the oxalateof ammonia’as a test for the lime ; the oxalicacid combines with the lime, for which ithas a strong affinity, and an oxalate of limeis formed, which is also insoluble. The

well-digger’s test of the purity of water is agood one ; he uses a solution of soap to trythe quality of the water obtained at differentdepths. A solution of soap in spirit of wine,if dropped into distilled water, leaves noprecipitate ; but if the water contain sul-phate of lime, it will occasion a white floc-culent adhesive precipitate. Some of thesprings about London give you almost a

saturated solution of the sulphate of lime ;such water is very harsh and disagreeable

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to the taste, is very unhealthy, probably,and very unfit for washing, or for pharma-ceutical or manufacturing processes.

Sulphate of lime is decomposed by thecarbonated alkalies, so that if you boil itwith carbonate of potash, you obtain a sul-phate of potash and a carbonate of lime. Inits crystalline form, called selenite, and lamel-lated, called gypsum, it is found in the blueclay about London. The crystals are rhom-boidal, and I believe that the rhomboidalprism is the primitive form. Here is a spe-cimen of the anhydrous sulphate, containingno water of crystallisation, and is a rare

mineral; and the Florentine artists are inthe habit of using it occasionally for smallworks of sculpture. Whenever the crystal-lised salt is heated, it crumbles down, and isthen called plaster of Paris. All the varie-ties of gypsum, alabaster, and so forth, are

only coloured varieties of the sulphate oflime.When phosphorus and quick lime are lieated

together, dark chocolate-coloured substanceis obtained, which is phosphzcret of lime; it is

probable, however, that what is called aphos-phuret of lime, is, in fact, a phosphuret ofcalcium. When thrown into water, phos-phureted hydrogen gas is evolved, phospho-rous and hypo-phosphorous acids are formed.and phosphite and hypo-phosphite of lime leftin solution in the water ; but these have notbeen particularly examined. The best modeof making this compound, is to put the

phosphorus into an earthen-ware tube ofabout eighteen inches in length, and an inchin diameter ; the phosphorus should be putinto the bottom of the tube, which mav thenbe filled up with pieces of clean quick-lime,which should be broken into small pieces.The tube should then be put into a furnacein the inclined position, so that the end con-taining the phosphorus may protrude ; whilethe upper part of the tube is heating to red-ness, draw the tube slowly into the fire, bywhich the phosphorus will be volatilised,and by combining with the red hot lime,will convert a portion of it into phos-phuret. The tube should be coated withclay, and, after the process, should be care-fully corked until cool, when the brownpieces are to be selected and kept in wellstopped bottles. The stench produced bypouring’ phosphuret of lime into the holesby which the water is turned on in thestreets of London, was caused by the decom-position of the phosphuret, which trick wasplayed off by some of the persons who areadverse to the introduction of gas lights,thus trying to make people believe that thestench issued from the gas ; but it was a

very foolish and expensive trick, by whom-soever it was played off.The phosphates of lime are four or five in

number, but that which consists of one proportional of litne, and one proportional of

acid, constitutes the hardening ingredientof bone, and is the substance resorted to forthe production of phosphoric acid. Phos-phate of lime exists native, constituting amineral, of which there is a very great va.riety, to which various names have beengiven. My opinion, however, is, that che.mical nomenclature should be applied as faras possible, to mineralogical compounds, asthey are found in Nature ; whereas a numberof confusing names have been applied to

them, depending upon their colour, shape,and other properties ; and lately, mineralo.gists have taken it into their heads to call !minerals after the names of different per.sons, than which nothing can be more ab.surd; thus they have Tliomsonite, Jack.sonite, Childrenite, and a half hundred ofothers. Here is a specimen of the native

crystallised variety, of singular beauty, fromDevonshire; here another from Cornwall.Here is a specimen of the asparagass stone,or green native phosphate, from Bohemia.Here is a specimen from Spain, which, whenheated, exhibits a beautiful green light.

This brings us to the carbonates of lime, avery important class of bodies, so important,that it is embarrassing to condense their che.mical history into the necessary limits. Thecarbonate of lime may be procured by pre-senting a solution of carbonic acid to a solu.tion of lime, and I shall show you this modeof forming it. Now, in the fnst place, ifwe get carbonic acid and lime-water together,the carbonic acid readily combines with thelime, and converts it into a carbonate oflime, and you have carbonate of lime, or

chalk, precipitated : this is the direct for-mation of it. If you take a solution of car-bonic acid, and add to it a solution of lime,you obtain a similar result; but, you willobserve, that if you add an excess of acid,this precipitation disappears, the carbo-nate of lime being again dissolved by theexcess of acid, and a considerable quantityof carbonate of lime may be taken up inthis way. This experiment, then, will ex-plain to you why it is that many springscontain a large quantity of carbonate oflime, which is held in solution in the waterby excess of carbonic acid, and why thewater deposits the carbonate of lime as thecarbonic acid escapes ; such are called pe-trifying springs, and baskets, and other

things, immersed in the water of the spring,become coated with the carbonate of lime,as is especially the case at Matlock, in Der-byshire, where the carbonate forms finestalactites, admitting of a beautiful polish.The pipes used for the conveyance of waterare sometimes coated with such a quantityof the carbonate, that the wood of the pipemight be removed, and its continuity pre-served, by the incrusted carbonate. (Speci-

Mons of this kind were shown.) These are

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so many instances of the solution of carbo-nate of lime in excess of acid, and of themanner in which it is deposited. You haveseen that when we precipitate a salt of limeby carbonic acid, we obtain a carbonate oflime ; but as it exists in such abundance innature, we never have recourse to artificialmeans for its production. Now, with re-gard to the natural forms of this substance ;you have it massive or foliated, in differentforms of marble ; you have it in the form ofstalactite, or stalagmite ; you have it in dif-ferent kinds of marl, and in several clays :and when you recollect that chalk is nearlya pure carbonate of lime, being mixed

only with a little argillaceous earth ; andwhen you also recollect, that there are largemountains of lime-stone, which is also a car-bonate of lime, you will see what immensequantities of this substance there are innature.

It becomes our business now to establishthe composition of carbonate of lime ; andit is composed of 28 parts of lime and 22 ofcarbonic acid ; consequently, it consists ofone proportional of lime and one of carbonicacid, and its equivalent number is 50. It

dissolves, as you have already seen, witheffervescence in the acids, and thus furnishesus with no bad means of determining thestrength of the acid employed, with whichit always forms saturating compounds. If

you take a piece of marble and weigh it,and pour on it diluted muriatic acid, youcan ascertain the strength of the acid, byascertaining how much of the carbonate oflime the acid will take up. Linae-stone is asubstance of great importance in the arts ;it gives us quick-lime when burnt, and thebase of many cements, forming a mortar

when mixed with sand, which has the pro-perty of gradually concreting until it be-comes as hard as stone. It is also of greatuse in agriculture, to say nothing of its or-namental applications, which are very nu-merous. The fact is, that lime is one of themost important manures which we possess ;and although I cannot at present enter uponthe nature of its action. I may sive you ageneral notion of its use by saying, thatquick-lime has the power of acting on ani-rnal and vegetable substances, so as to ren-der them soluble in water, and it is in thisway that the different vegetable and animalsubstances are rendered fit for the nourish-ment of plants, the lime itself becominginert and forming a valuable part of thesoil. The lime, therefore, ought to be ap-plied to the soil, or mixed with the othermanure, as quickly as possible after it comesfrom the kiln ; and, hence, the great impro-priety of leaving heaps of it about fields, aayou often see done, by which it loses its

activity and usefulness ; but this will beentered into more by and by, when con-

sidering the action of lime upon vegetableand animal bodies.

Boracic acid combines with lime, andforms a mineral called boracite, of no greatimportance. Our time will not allow us to-

day to conclude the subject of hme, by con-sidering the compounds which it forms withfluoric acid, as I intended to have done. Ishall, therefore, defer it until the next lec-ture, and conclude the present by mention-

’ ing to you some of the means by which thepresence of lime may be detected. Here is asolution of lime in muriatic acid, a solution,

in fact, of chloride of calcium. Now one

of the readiest tests of the presence of lime1 is oxalate of ammonia, or oxalic acid, which,when added to a solution of lime, occasions. in it a white precipitate, which is oxalate

of lime ; and if this precipitate be collectedand heated, the oxalic acid, being a vege-table product, is easily destroyed by theheat, and you have the lime left in a purestate. When you want to know the quan-tity of lime in any solution, precipitate itby oxalic acid, heat the precipitate red hotin a platinum cup, and you obtain the quan-tity of lime in the liquid. One of the cha-racteristics of lime is, that its salts are notprecipitable by caustic or pure ammonia,but, if you add the carbonate of ammo-nia, then you get a carbonate of lime. Nowit often happens, that lime is held in solu-tion bv substances which are precipitable bvammonia, and if you then use the carbonatesof potash or soda you will obtain a carbo-nate of lime. With regard to the insolublesalts of lime, they are decomposed by theaction of carbonate of potash and heat, and acarbonate of lime will be formed which maybe precipitated from its solution by purepotash. Pure ammonia does not precipi-tate the salts of lime from their solution-pure soda and potash do. A great manyother tests of lime may be resorted to, butthere are none more effectual.The nature of ftuor spar, and the other

compounds of lime with fluoric acid, will beconsidered in the next lecture.

FOREIGN DEPARTMENT.

Experiments on the Electricity of the Blood, theUrine, and the Bile of Animals, in a healthyand diseased state. By F. BELLINGERI.*

* Annali Universali di Medicina, April,1827.

The following are the conclusions to whichthis physician has arrived.

1st. That venous blood in oxen, sheep