Note on Nitrite of Soda,* by Mr. W. D. HOWARD. products. In fact, I took all the compounds which, by MR. WARINGTON'S able paper in the Pharmaceutical Journal for July has pretty much exhausted this ject. I do not, however, remember to have seen noticed a tolerably ready method for purifying the rough nitrite of soda from much of the undecomposed nitrate which in practice it always retains. This method consists in taking advantage of the slight difference in solubility between the two salts, which is sufficient to enable the nitrate to be in great measure removed before the nitrite begins to crystallise out. A sample of rough nitrite treated in this way, which originally contained 18.9 per cent. of nitrite of soda, was purified till it yielded 40°3 per cent. As the crude nitrite invariably contains either carbonate of soda, caustic soda, or a mixture of both, this method will not alone enable a perfectly pure product to be prepared. reason of their chemical composition or their physical sub-properties, their chemical or their capillary affinity, will combine or unite mechanically with lime. I equally desired to determine the condition of the lime which is best suited for the puzzolanic action. TECHNICAL CHEMISTRY. Chemical Researches on Hydraulic Cements, by M. E. FREMY. (Continued from page 153.) Action of Fat Lime on Various Bodies.—If in the calcination of an argillaceous limestone aluminate of lime is produced, the hydraulic properties of which cannot be doubted, there is also formed, without doubt, during the calcination, a silicate of lime and a silicate of alumina and lime, which, as we know, gelatinise with acids, but do not hydrate in water. Must it be admitted that silicate of lime and the double silicate of alumina and lime, which exist in all hydraulic cements, play no part in the setting of cements in contact with water? I think not; and the following experiments seem to confirm this opinion. I have already said that these silicates exercise no direct action upon water, and cannot in this respect be compared to calcareous aluminates. But a cement after its calcination contains free lime; aluminate of lime, by decomposing in water, may also produce it. I considered that this base might perhaps exercise an action upon bodies which do not immediately hydrate, and cause them to play the part of puzzolana. It was on account of this hypothesis that I undertook the following experiments on the composition and properties of the puzzolanas: The first thing I had to ascertain was whether, in cements and mortars, lime acts otherwise than by obsorbing the carbonic acid of the air or in forming a hydrate which solidifies whilst drying. We know that lately the chemical action of hydrate of lime on puzzolanas has been strongly contested. My experiments leave no doubt on this point, and show that there really exists a certain number of bodies which, when cold, form a combination with hydrated lime, and produce masses which solidify in water. To determine the nature of the bodies which possess this remarkable property, I took almost all the natural and artificial compounds which by nature form combinations with lime. I mixed them with variable quantities of anhydrous or hydrated lime. The bodies principally experimented on were silica and alumina in their various states, clay dried and baked at different temperatures, baked earths, natural or artificial silicates, the principal rocks, insoluble phosphates and carbonates, bodies remarkable for their porosity, such as animal charcoal, and several manufacturing * Read before the Pharmaceutical Conference. formed by carefully hydrating the lime, and which may My experiments showed that the compound which is be thus represented CaO,HO, is that which, under the influence of water, combines with the puzzolanas with the greatest facility. I have shown besides that true puzzolanas-that is to say, those which form a combination with hydrate of lime when cold, solidifying in water-are much rarer than one would imagine. Baked earths, volcanic substances, more or less calcined clays which are generally considered as puzzolanas, should not be comprised in this class of bodies, and, with a few exceptions, do not harden on their contact with hydrate of lime. The really active bodies, the true puzzolanas, are the simple or multiple silicates of lime, which only contain 30 or 40 per cent. of silica, and which are sufficiently basic to gelatinise with acids. As these good hydraulic cements contain the very basic, simple or multiple, silicates which gelatinise with acids, I have been led to admit that the part of these bodies in the setting of cements is to act as puzzolanas, and combine, under the influence of water, with the free lime which exists in cements. These observations coincide exactly with those of M. Chevreul, in which he has shown that puzzolanas unite with lime on account of a phenomenon of capillary affinity. After having studied the properties and composition of the different elements found in cements, I sum up the theory of their hydraulicity in the following propositions: I do not admit what is still generally believednamely, that the setting of hydraulic cements is due to the hydration of silicate of lime or that of double silicate of alumina and lime. These salts form no combination with water. I attribute the setting of a hydraulic cement to two chemical actions:-1st, to the hydration of aluminates of lime; and, to the reaction of hydrate of lime upon the silicate of lime and the silicate of alumina and lime which exist in all cements, and in this case act as puzzolanas. The calcination of an argillaceous limestone produces a good hydraulic cement only when the proportions of clay and lime are such that they form, in the first place, an aluminate of lime, represented by one of the following formula: Al,O,,CaO–Al,O,,2CaO–Al2O,,3 CaO; in the second place, a very basic simple or multiple silicate of lime, which gelatinises with acids and approximates to the following formula: SiO,,2 CaO–SiO3,3 CaO; and thirdly, free lime, which may act upon the preceding puzzolanic silicates. In many cases the chemical composition of an argillaceous limestone is not the only condition which determines the quality of the cement; the reaction of the lime upon the clay must take place at the highest temperature. Indeed, this excessive heat produces the hydraulic elements of the cement in the basic conditions which the setting in water requires, and which by melting the aluminate of lime gives it all its activity. Such are the relative theoretical conditions of the hydraulicity of cements which result from the experiments of this first research. In another paper I shall show the practical utility of these researches. PHARMACY, TOXICOLOGY, &c. On the Purity of Commercial Bromides and Iodides other than Iodide of Potassium,* by HENRY MATTHEWS, F.C.S. NINETEEN samples of bromides and iodides were examined, consisting of seven samples of bromide of potassium and three each of the bromides and iodides of ammonium and cadmium. The results of the analyses are given in the tables annexed. Water 1.69 0.8 0'74 0.96 O'22 VII. and afterwards heating a weighed portion of that precipitate in a current of chlorine. Bromine in the iodides was searched for qualitatively by mixing a portion of the salt, dissolved in water, with dilute sulphuric acid and a little starch-paste, adding fuming nitric acid, and then chlorine water, until the blue colour produced by the iodine and starch disappears. The further addition of chlorine water will now liberate the bromine, if present, and it may be removed by means of chloroform. No bromine, however, was found in any of the samples of the iodides. 4. Water. By heating in the air-bath, at a temperature of 120° C., until a constant weight was obtained. The results to be deduced from the analysis are, that 025 the bromides of ammonium and cadmium and iodide of 051 cadmium are practically pure. The same cannot be said of the bromide of potassium; and with regard to the iodide of ammonium, the principal impurity is the large quantity of sulphate found in two of the samples, and trace 0'7 2.II 0'04 0'51 1. 92 97 93.86 91.66 100'04 98.71 95.86 the presence of which in such quantities is somewhat difficult to account for. Sulphate. trace 2.99 Bromate 0'44 0.8 Bromide 97.46 92.85 96.9 Carbonate 100'25 99'72 99.65 Sulphate. 6993 Iodide of Cadmium. III. The whole of the samples, with the exception of five forwarded to me by Dr. Attfield, were purchased at the shops of well-known chemists and druggists, and varied very considerably in price, the highest priced not being always the purest. Notes on a Commercial Sample of Sulphate of Quinine,† by W. W, STODART, F.G.S., Bristol. IN July last I received a sample of sulphate of quinine from Dr. Attfield, which was forwarded for the inspection of the Adulteration Committee, and a report requested. The name of the manufacturer, as stated on the label, was Auguste Thil, at Paris. I could get no information from many of the leading drug-houses in London, in answer to inquiries respecting its commercial relation and importation, nor could I obtain an original bottle till a friend bought one for me from a druggist at Cardiff. As far as I can ascertain, it is principally sold for the use of shippers and surgeons, and, as an induce009 ment to the purchaser, is offered at a low price. In external appearance it differs much from a pure article, 0'17 0'4 027 such as Howard's or Pelletier's. It is not so distinctly 99'68 99'58 99.61 crystallised, and is more silky. It is much more soluble in diluted sulphuric acid than the genuine salt. It is not discoloured by strong nitric or sulphuric acids, showing the absence of phloridzine or salicine. trace Iodide of Ammonium. I. III. I. II. 6.02 Iodate 0'07 99'96 99.84 100'00 99'93 99'98 99'97 The methods adopted for the determinations were1. Carbonate. By a standard solution of sulphuric acid, 10 cubic centimetres of which were equivalent to o'05 grammes of KO,CO2. 2. Sulphate. In the usual way, by precipitation with chloride of barium. 3. Chloride, bromide, and iodide. In the bromides about 2 grammes of the salt, dissolved in water, dilute nitric acid added, and then agitated with chloroform, more chloroform being added until the chloroform remained colourless. The chloroform is well washed with distilled water, and the chlorine and bromine determined in the aqueous solution by precipitation with silver, and afterwards heating a weighed portion of the precipitate in a current of chlorine. The iodine was determined by deducting the weight of the silver precipitate obtained after the removal of the iodine from the weight of a corresponding silver precipitate obtained from a portion of the original salt. In the iodides, the chlorine and iodine were determined by weighing the precipitate by nitrate of silver, * Read before the Pharmaceutical Conference. An aqueous solution of chlorine and ammonia failed to give the green tinge so characteristic of quinine. Nitrate of silver and nitric acid gave a white curdy precipitate of chloride of silver. Chloride of barium and hydrochloric acid also gave a dense precipitate of sulphate. The next test applied was that of Dr. Herapath. Ten grains of the suspected salt, treated in the usual iodosulphate-a quantity too small to be weighed. I way, only afforded one or two very minute crystals of then tried the sulphocyanide test described by me at our last year's meeting. The resulting precipitate, under a quarter-inch lens, showed abundance of large massive crystals of sulphocyanide of cinchonine interspersed with the well-known tufts of sulphocyanide of quinidine, but none of the long acicular crystals of the quinine salt. When dissolved in water, to the extent of a scruple to the ounce, in daylight. Even the spark of a powerful Ruhmkorff's hardly any fluorescence was perceptible to the naked eye coil gave only a faint fluorescent light, which is so in t Read before the Pharmaceutical Conference. tense and beautiful in a solution of quinine, even when containing only the one-fourth of a grain per cent. My modification of Liebig's test was most decisive, and corroborated the above results in the most marked manner. I cannot proceed without passing a vote of censure against the British Pharmacopoeia test. The amount of water is very prejudicial to its usefulness, nor is there any rule given for the quantity of ammonia to be used, and the student will find to his vexation that, as the quantity of ammonia used differs, so will the amount of precipitate vary also. Another thing worthy of remark is, that the presence of cinchonine modifies and almost entirely masks the iodine and sulphocyanide tests for quinine. I could not get the herapathites to crystallise, or the sulphocyanides to deposit, till I had separated the quinine by ether. If I had not, therefore, been aware of this, I should have put down this specimen of quinine to have had none at all in it of the true alkaloid. The best use to make of the Pharmacopoeia method of testing is to correct any previous observation by a synthetical examination, for either of or any mixture of the three alkaloids, when treated exactly alike, show a marked distinction in their general appearance when too much ammonia is not employed. A quantitative analysis gave 413 per cent. of cinchonine, which would be equivalent to 36 31 of the sulphate, the remainder being quinidine and quinine, the latter forming about 10 per cent. of the whole, and probably a mixture of hydrochlorates and sulphates. From the foregoing experiments it is evident that the so-called sulphate of quinine is nothing of the kind, but a mixture of cinchonine and quinidine, with only a tenth of quinine. In short, it is truly what the label ironically states, a "fabrique spéciale," which it is the duty of the Adulteration Committee to expose, and certainly not proper for a druggist to sell as pure sulphate of quinine. On the other hand, it is very pleasing to find that such an article could not readily be procured from our well-known wholesale London houses. It proves the truth of what I affirmed at Bath, that it is the druggist's own fault if he does not get a genuine article. On the Iodo-Hydrargyride of Potassium and the Oxidation Tests for Methylic Alcohol in the Presence of Ethylic Alcohol and some other Organic Bodies,* by Mr. JOHN TUCK. AT the Bath meeting of the British Pharmaceutical Conference, it was shown that oil of cloves had the same effect on the iodo-hydrargyride of potassium test for methylic alcohol as acetone; it therefore became evident that some additional experiments were necessary, in order to determine whether or not the volatile oils or organic principles existing in the tinctures were in any way calculated to interfere with its application, and if so to devise some simple method whereby such interfering agent might be removed previous to the application of the test. With this object in view, I dissolved one drachm of the oil of cloves in nine drachms of spirit of wine; on testing this with the iodo-hydrargyride of potassium, as I expected, there was no precipitate. I next distilled a portion of it, and on testing the distillate I obtained the reaction characteristic of spirit of wine. This experiment teaches us that the worst possible interfering agent can readily be separated by simple distillation. I have also distilled and tested nearly the whole of the tinctures of the British Pharmacopoeia prepared with • Read at the Pharmaceutical Conference. duty-paid spirit, and in no case have I met with any oil or organic principle that interfered with the test. I obtained the characteristic precipitate in every case, so that the absence of a precipitate with the iodo-hydrargyride of potassium test may be looked upon as conclusive evidence of the preparation being made with methylated spirit. The tinct. gallæ requires to be distilled carefully, otherwise some portion of the formic acid is carried over with the vapour of the spirit, and on testing it a dark precipitate is the result. În distilling tinct. iudi co. some portion of the iodine is almost sure to be carried over; but if the distillation is conducted with care the small portion that is carried over will not interfere with the test; however, if thought desirable, this may be prevented by adding potash to the tincture previous to distillation. Since the reading of my former paper at Bath, a process has been published for the detection of methylic alcohol in the presence of ethylic alcohol and volatile oil by Mr. Miller, which is certainly the best and most reliable of all that have been brought forward. I do not, however, mean to say that any new principle has been discovered, or the new application of an old one, for even when the methylated spirit in question was under the consideration of the Board of Inland Revenue, Professors Graham, Hofmann, and Redwood reported to the Chairman that,— "Under the influence of oxidising agents, methylic spirit furnishes, together with other products, a considerable amount of formic acid, whilst alcohol under these circumstances yields principally acetic acid. Formic and acetic acids, although closely allied in composition and general characters, still offer a greater number of points of difference than the two alcohols which they represent. Formic acid may be readily distinguished from acetic acid by the facility with which the former precipitates the metals from the solutions of the more easily reducible metallic oxides, such as oxide of silver and oxide of mercury, which are not affected by acetic acid. Unfortunately, this method of testing became inapplicable, since it was found that alcohol free from methylic spirit when submitted to the action of oxidising agents, invariably yields, in addition to aldehyde, which can be resinified and removed by potash, a small quantity of the products of oxidation of a suspected liquid cannot with formic acid, so that the presence of formic acid among certainty be regarded as an evidence of the existence of methylic spirit in the original liquid." The method adopted by Mr. Miller in applying the principle of oxidation is not capable of being carried out easily nor quickly, but these disadvantages are counterbalanced by the certainty which attends the results of the oxidation of methylic alcohol. As stated by the learned chemists in their report to the Board of Inland Revenue, the presence of a small quantity of formic acid in the oxidation products of a suspected liquid is no proof of the existence of methylic spirit in the original; but, as ethylic alcohol only yields a very little, and as methylic alcohol yields a great amount of formic acid, its presence in quantity after the oxidation of a small portion of a suspected spirit, by whatever method it is conducted, points unmistakably to the previous presence of methylic alcohol, other sources from which it may possibly be derived of course being absent. The sources from which formic acid may be derived by oxidation without the presence either of ethylic or methylic alcohol are many, so that in every case, before applying any method of oxidation to a suspected spirit, we should first free it from organic matter by distillation or other process,-albumen, casein, gelatine, starch, to be present in these beverages; whether there is a sugar, both cane and grape, tartaric acid, woody fibre, certain amount of sweet nitre added to the methylated the cereal grains, and many other organic substances spirit, or whether it arises from the addition of nitric yielding formic acid by oxidation; it also exists, as is acid to the spirit, and then boiling or distilling it, is very well known, naturally in ants, some caterpillars, oil of difficult to say. I am rather inclined to believe that the turpentine, the stinging-nettle, and, it is said, even in latter is the true origin of it, and that the nitric acid is some mineral waters. added with the intention of oxidising the oils in the The method given by Mr. Miller in the Pharma-naphtha, or at any rate modifying the taste and smell of ceutical Journal for last April is as follows:-"Put the plain methylated spirit. The three specimens of into the flask thirty grains of bichromate of potash, in "whiskee" differ much from each other, the medicated powder, add half an ounce of water with twenty-five whiskee contains a good deal of sweet nitre, and is minims of strong sulphuric acid, and then half a fluid strongly acid, the sweetening agent here used is sugar, drachm of the spirit; allow the mixture to stand fifteen and it is the least sweet of all the beverages; the minutes, and distil half a fluid ounce. Add to the dis- "Hollands flavoured whiskee" is acid, and, like the tillate a very slight excess of carbonate of soda, boil it others, contains a portion of sweet nitre, and is down to two fluid drachms, and add enough acetic acid sweetened with honey. I now come to the last, the best, to impart a distinct though feeble acid reaction; then and the most remarkable of this series of specimens pour it into a test-tube, and, after adding a grain of illustrating human ingenuity in cheating the Excise, nitrate of silver, dissolved in half a drachm of water, the "Pure Islay Mountain Medicated Whiskee;" this boil very gently for about two minutes. If the liquor was at first a colourless and perfectly clear syrupy liquid, merely darkens a little, but continues quite translucent, which, on being exposed to full daylight in a window, the spirit is free from methyl; but if it becomes muddy during some very cold weather, became turbid, and and opaque, and the tube, after being rinsed and filled gradually deposited a. lot of flooculent crystals. Not with water, appears browned (best seen by holding it being at that time at all able to understand the formaagainst white paper), the spirit is methylated." tion of these crystals, I forwarded to our worthy President, Mr. Deane, two or three drops of the thick crystalline deposit, for him to examine them microscopically; after the examination, both chemical and microscopical, of this small quantity, he felt quite assured that the source of the crystals was honey. Since that time, there has been a greater deposit of these crystals, a specimen of which is on the Conference table. I have chemically examined them, and have come to the same conclusion as Mr. Deane; these crystals are, without any doubt, grape sugar, and in all probability derived from honey, which must first have been dissolved and then decolourised, for the finest sample of honey I have yet seen would certainly impart some degree of colour and turbidity to any solvent, and this specimen of "whiskee" was quite colourless and perfectly clear. Although acid, it is by no means so much so as the other specimens, and it seems also to be flavoured with a slight portion of chloroform. The spirit used in its fabrication must have undergone some kind of "cleaning" process, as this is the most pleasant beverage of the whole series. On distilling a portion of it, and applying the iodo-hydrargyride of potassium, and the oxidation method of testing the presence of methylic alcohol was thoroughly proved. The compounding of these intoxicating drinks, for it is a sham to call them by any other name (for they certainly are neither "medicinal" nor "cordial," no more than duty paid brandy, gin, or whisky), is a direct fraud upon the revenue, was never contemplated or intended to be one of the uses of methylated spirit, and should be strongly discountenanced by all honourable men. The Board of Inland Revenue liberally allows the methylated spirit duty free for the arts and manufactures; and all interested in their welfare-and who is not ?-should protest by their words and deeds against the abuse of such a great boon. I distilled a portion of the tinct. rhei, of which I have brought a sample, and on testing the distillate with the iodo-hydrargyride of potassium, there was no precipitate, thus indicating the presence of methylic alcohol. On carrying out the oxidation method of detecting it, I obtained further evidence of its presence, thus confirming the reliability of the iodo-hydrargyride of potassium, and proving, beyond all dispute, that the tincture was a methylated one. If a method of oxidising the methylic alcohol and of neutralising the acid so formed could be devised, without distillation, it would wonderfully simplify the oxidation test; although I have made some experiments in this direction, by heating the methylated spirit with a mixture of lime and potash, they have not yet been of a satisfactory nature. I have not tried the action of platinum black on methylated spirit, but presume it would slowly convert the ethylic alcohol into acetic acid, and the methylic into formic acid. According to Dobereiner, spongy platinum, moistened with wood spirit, does not act upon the air, but if moistened at the same time with strong caustic potash, it often becomes heated to redness, and converts the wood spirit, first into formic, and afterwards into water and carbonic acid. As being very suitable to the present paper, and thinking, too, they would prove of interest, I have pleasure in placing before Conference eight different specimens of methylated preparations, kindly placed at my service by the Chairman of the Board of Inland Revenue, W. H. Stevenson, Esq. There are three specimens of the beverage called called "whiskec," three of "brandee," one tincture of rhubarb, and one sweet spirits of nitre. The specimens of "brandee " are all prepared with methylated spirit, without any, or at any rate but little, preparatory cleaning, and are all distinctly acid. The "Medicated Indian Brandee," and the "Cordialised Indian Brandee," are all sweetened with sugar, the French brandee or Indian tincture is different to the other two, being much higher flavoured; it is made very sweet with honey, and, I believe, contains saffron as a flavouring ingredient; the colour is derived from burnt sugar; and they all contain more or less sweet nitre. I am not at all prepared to say, positively, in what manner the sweet spirit of nitre comes To sum up this paper in a few words, I think we may now look upon the question of the "detection of methylated alcohol in the presence of ethylic alcohol and organic bodies " as thoroughly and satisfactorily answered. We can, in the first place, readily detect the acetone, which is always associated with the methylic alcohol, and by the oxidation method of testing, interfering bodies being absent, the methylic alcohol itself. PROCEEDINGS OF SOCIETIES. ROYAL INSTITUTION OF GREAT BRITAIN. Weekly Evening Meeting, Friday, April 7. H.R.H. THE PRINCE OF WALES, Vice-Patron, in the Chair, On the Combining Power of Atoms. By Dr. A. W. HOFMANN, F.R.S. YOUR ROYAL HIGHNESS, LADIES AND GENTLEMEN,-You observe on the lecture-table a great number of bottles, containing an almost perplexing variety of chemical substances; the walls of the theatre are covered with diagrams exhibiting an endless number of formula, which some of my audience, I have no doubt, are contemplating with mixed feelings of uneasiness and resignation. Nor will it diminish your discomfort if I tell you that each of the substances on the table represents at least a thousand bodies actually known, and again that each of the known bodies represents a million or more bodies which are not known, but which exist well defined in the mind of the chemist, who calls them into life whenever he requires them for purposes theoretical or practical. At the first glance, I admit this is rather a formidable array; but our anxiety is materially lessened, if we learn that this host of substances is formed according to simple laws which it is in our power to discover, and which by the united efforts of chemists are gradually unfolding themselves. May I be permitted this evening to call your attention to some of the laws, or at all events law like regularities, recently observed, and which are at present engrossing the interest of the leading chemists of all countries ? I would commence with one of the simplest of experiments: Here are two gases, hydrogen and chlorine, the one a colourless inodorous gas, which burns quietly with a pale flame, the other a greenish yellow gas, possessing a suffocating odour, and not inflammable. When equal volumes of these two gases are mixed together, and a light applied to the mixture, an explosion takes place, a compound gas being produced, which fumes in the air, and which, when dissolved in water, constitutes the spirit of salt, or muriatic acid of the earlier chemists, now called hydrochloric acid. By certain processes, which we must not inquire into at the present time, the compound of hydrogen and chlorine, called hydrochloric acid, may be made to unite with another gas, oxygen; the combination giving rise to the formation of an acid called hypochlorous acid, and by which most of the bleaching operations carried out in commerce are effected. On plunging an appropriately prepared piece of Turkey-red calico into a warm solution of chloride of lime, which is closely related to hypochlorous acid, you observe that a white pattern is produced on the cloth. Again, an additional quantity of oxygen may be united to hypochlorous acid, when the compound called chlorous acid is formed. A well-known salt of commerce, chlorate of potassium, is generally used for its preparation. This salt is readily decomposed by acids. The explosive violence with which sulphuric acid acts upon it, the detonation attended by flashes of light, are phenomena early and frequently observed by the laboratory student. By substituting nitric for sulphuric acid, an explosive gas is formed, which, when dissolved in water, constitutes the chlorous acid in question. A third compound, chloric acid, may be formed by the addition of a further dose of oxygen to chlorous acid. The most familiar salt of this acid is the chlorate of potassium just mentioned. This, as well as other derivatives of chloric acid, is largely used for pyrotechnic purposes. Here we must be satisfied with calling attention to a species of white gunpowder which has been lately devised, and which consists of a mixture of the potassium salt with tannic or gallic acid. Lastly, by still further increasing the supply of oxygen, a fourth compound, perchloric acid, is produced. This substance again exhibits the explosive habitudes of the group of bodies in question. When made to combine with aniline, for instance, perchloric acid gives rise to a compound which goes off when heated in a test-tube, burning, as you observe, with an intense white light. A glance at the diagram shows us the regularity with which the amount of oxygen increases in this series of Oxygenated derivatives of hydrochloric acid. There is nothing arbitrary in this succession; each increment ensues step by step. Increment of Oxygen. Hydrochloric acid Hypochlorous acid. Chlorous acid Chloric acid Perchloric acid HCl + 0 = HCIO HC1+20 HCIO2 HC1+30=HCIO, HCl +40 HCIO = Looking at the simplest body at the head of the list, we find it to be a compound of one atom of hydrogen with one atom of chlorine. By uniting this compound with one atom of oxygen, we obtain hypochlorous acid; by adding another we produce chlorous acid; the accession of a third atom gives rise to chloric acid; and a fourth atom of oxygen, lastly, produces perchloric acid. The same gradual rise in the successive additions of oxygen may be traced in numerous other groups of bodies. For the present we will confine our attention to two more series. Under the name of olefiant gas, a transparent colourless gas, burning, as you observe, with a brilliantly luminous flame, is known, which consists of carbon and hydrogen. By a circuitous process, which must not detain us, this of a pungent odour, which chemists have called aldehyde. gas may be converted into a peculiar very volatile liquid This substance, which is more readily procured by sublooked upon as a compound of olefiant gas with oxygen. mitting alcohol to the action of oxidising agents, may be Aldehyde is marked by its powerful attraction for oxygen; impossible to preserve aldehyde except in hermeticallyso greedily, indeed, does it absorb this gas that it is almost closed vessels. Nor does aldehyde unite only with oxygen when it meets with it in the free state; combined oxygen is equally attracted by it. When gently heated with oxide of silver, dissolved in a suitable liquid, aldehyde very rapidly removes the oxygen from the oxide, metallic silver the vessel in which the operation is performed. in a lustrous condition being deposited on the surface of This reaction, first observed by Baron Liebig many years ago, has recently been modified so as to admit of industrial application on a large scale for the manufacture of lookingglasses and reflectors for astronomical instruments. When aldehyde is thus oxidised, it is converted into a compound constituent of common vinegar. called acetic acid, well known to every one as the principal tional quantity of oxygen to produce a compound called Again, acetic acid may be made to unite with an addiglycolic acid, an acid which has been discovered during the last few years, but which has not at present received any useful applications. simple relation existing between these four bodies:On referring to the following diagram, we perceive the Increment of Oxygen. Olefiant gas Aldehyde Acetic acid Glycolic acid C2H+ O=C2H2O CH+20 C2H2O2 C2H+30= C2H2O, We observe here exactly as in the previous series the gradual assimilation of oxygen. Olefiant gas by absorbing one atom of oxygen produces aldehyde; by absorbing a second atom it gives rise to the formation of acetic acid; by a third annexation of a similar quantity of oxygen; lastly, glycolic acid is formed." |