DR. SHERIDAN 3IUSPRATT Jan. 15> 1849. Cdonel Philip Yorke in the Chair. The following presents were announced :-“ On the Phosphoric Strata of the Chalk Formation,” by Messrs. J. &I. Paine and J. T. Way from the authors ; “ Report on the Ana1yvL.k of the Ashes of Ylailts,” Part III. by Nessrs. J. T.Way and G. Ogston from the authors. The followi iig cornmui~icationsmere read V.-On the Salts of Selepzzious Acid. By DR.SHERIDAN MVSPRATT Professor to the Livelyool College of C1hemisti.y. PRELININARY REMARKS. I undertook the investigation of the salts of selenious acid with the view of ascertaining whether they were analogous to those of sulphurous acid . Mitscherlich has remarked that the selenic and sulphuric acids are not only analogous in composition and in many of their pro- perties but that the similarity runs through their salts which resemble one another in chemical comportment constitution and form.We might infer from this that the selenites and sulphite; would be isomorphous sulphur and seleniuni being so analogous. In a former paper>* I mentioned the great similarity betmeen carbon and sulphur which also extends to the carbonates and sulphites. For nearly every carbonate I obtained a corresponding sulphite. The formulz of the three acids are appended in order to show their striking analogies Carbonic acid . . I GO Sulphurous acid . . 0 so Selenious acid 0 . SeO,. We see on referring to the above that they all contain the same amount of oxygen i. e. 2 equivs of oxygen united to cither carbon sulphur or selenium.Although I proved the isomorphism with regard to the first two my results with selenious acid are only in a few cases similar to those with sulphurous acid. One of the great cmses of this may be the persistency of the former and the instability of the latter. There were numerous difficulties to contend with in the preparation and analysis of the salts of this acid as will be hereafter mentioned. * Liehig’s hiii~alender Chemie Bmd I,. p. 239. ON THE 8-4LTS 03 BELENIOUS ACID. PREPARATION OF THE ACID. Selenium was dissolved in pure fuming nitric acid and the solution evaporated on a sand-bath to dryness. The nitric acid when added caused a most violent action large quantities of nitrous fumes being disengaged.The residue mas a white powder possess- ing a sour and styptic taste which heated on a sand-bath afforded as a sublimate most magnificent silvery-looking very long four-sided needles of selenious acid. This acid is also formed by acting upon selenium with aqua regia. The former method howcver is preferable. 9 Se + 6 NO = 9 SeO + 6 NO,. GENERAL PROPERTIES OF THE ACID AND SALTS. Berzelius has made allusion to many of the following properties of selenious acid and its salts. In some cases this illustrious Swede has not been sufficiently specific owing no doubt to the enormous number of facts he had to contend with in other departments of the Science. It is stated in Turner’s Chemistry,* ‘‘when su@hurous acid is added to a solution of selenious acid pure selenium is thrown down.” In the cold I could not obtain this reaction but when the two acids are mixed together and boiled a vermilion-coloured precipitate selenium separates.Strong hydrosulphuric acid decomposes selenious acid immediately in the cold an orange- yellow powder subsiding ; a sulphide of selenium. The preceding decompositions may be represented as follows SeO + 2 SO = Se + Z SO SeO + 2 HS = SeS + 2 HO. Hydrochloric acid has not the slightest effect upon selenious acid. Selenious acid is reduced when heated on charcoal before the blow-pipe the selenium imparting a beautiful blue colour to the flame. The fumes evolved are yellowish and ‘nave the smell of decayed horseradish ; a most characteristic test for the acid.The smell is so persistent that for days my clothes have retained it. This acid very seldom forms basic salts and then only with those metallic oxides which readily afford them with other acids. It easily produces a basic salt with oxide of copper in this respect materially differing from sulphuyous acid. On passing sulphurous acid into water holding oxide of copper in suspension a reduction takes place the sub-oxide of copper being formed. * Eighth Edition p. 265. DR SHERIDAN MUSPRATT 2 CUO + so = so + cu 0. When a selenite is heated in contact with any organic matter reduction inimediately occiirs ; great care has therefore to be exer- cised in the preparation of the salts not to allow any of the filtering paper to adhere to them.Charcoal reduces the salts immediately at a high temperature. If charcoal is fused with selenite of soda selenide of sodium and carbonic acid are obtained. +2 (NaO SeO,) + 3 C = 2 (Na Se) + 3 CO,. Chloride of ammonium distilled with a selenite affords selenium which condenses in the neck of the retort. The decomposition may be exhibited by the following equation 3 (NaO,SeO,) + 3 (NH,Cl) = 3 Se + 2 N + NH,O + 3 NaCl + 8 HO. Three equivalents of selenite of soda and 3 equivalents of chloride of ammonium contain the elements of 3 equivalents of selenium 2 of nitrogen 3 of chloride of sodium 8 of water and 1equivalent of oxide of ammonium. Selenious acid liquefies on exposure to the air. The neutral salts of selenious acid with potash soda and am-monia have a very caustic taste and react alkaline.They are extremely soluble in water. When aqueous selenious acid is neutralized by the alkalies and the liquid is treated with alcohol under certain circumstances an oily substance separates; this when kept for it long time becomes crystalline. Selenites of the alkalies are most difficult to prepare. They arc remarkably deliquescent and liable to undergo decomposition unless carefully dried over sulphuric acid. The neutral salts taste and react alkalinc. They dissolve with a slight reddish colour owing to a trace of reduced seleniuni; a remarkable circum-stance. Selenious acid ia extremely stable. When the crystals of the acid arc exposed to the air for weeks although they liquefy still I could not detect in them any selenic acid.How different is the case with sul- phurous acid which cannot be exposed to the air for an hour without a portion being converted into sulphuric acid. Sclenious acid accord- ing to Berzelius has a great tendency to form acid salts even in the relation of four of acid to one of base. I obtained a syrupy iiiass in one instance which when analysecl agreed with the statement above. I could not however obtain any qnadracid salt ON THE SALTS OF SELEWIOUS ACID. in a perfectly dry state. My intention in the present paper is to embrace all that is known respecting the selenites so that future investigators may have a full reference. I find as did Berzelius when an alkali is treated with selenious acid anti1 the liquid reacts neither acid nor alkaline that on evaporation crystals of a bisalt are deposited; a neutral salt remaining in solution.Rose has remarked that hyposulphite of ammonia only partially precipitates selenium in the cold; more is precipitated by boiling and still more on the addition of hydrochloric acid. In the cold the decomposition takes place extremely slowly if at all; on boiling however bisulphide of selenium is deposited-a large quantity is precipitated in the presence of hydrochloric acid SeO + Z (S 0,) = SeS + 2 SO,. When aqua regia is added to the bisulphide of selenium it is immediately decomposed. Boracic phosphoric and sulphuric acids expel selenious acid from its compounds at a high temperature.I employed sulphuric acid for this purpose in analysing the salts. Hydrochloric acid has not the slightest efect even when boiled with selenious acid; selenic acid however is reduced by it to the state of selenious acid SeO + HCl = SeO + HO + C1. Many of the salts of selenious acid lose their acid when heated; others part with only a portion and sowe do not evolve any as will be seen under the description of the various salts. SCLENITES OF POTASH. The neutral selenite is obtained by saturating carbonate of potash with selenious acid and evaporating quickly to dryness. I could not obtain the salt for a long time in a fit statc for analysis owing to there always being an excess of selenious acid. A definite salt is also extremely difficult to prepare 011 account of traces of selenium separating.Selenite of potash is remarkably soluble in water. It is almost insoluble in alcohol; but strange to say I could not precipitate it from its aqueous solution in a crystalline state by alcohol. An oily substance always appeared. It possesses a dis-agreeable taste is very alkaline to test-paper and deliquescent ; on which account great care has to be exercised in weighing the salt. 0.251 grms. salt gave 0.210 , sulphate of potash = 0.113 , potash leading to the fo'orniula KO SO,. Centesimally represented Theory. Exp. 1 ey. of selenious acid . 56 53.85 1 , of potash. . . 48 46.15 45.02 104 100~00 Biselenite of potash gives satiny-looking crystals.It is obtained by decomposing carbonatc of potash with an excess of selenious acid and allowing the solution to evaporate over sulphuric acid ;or by pre-cipitating the solution with alcohol in which menstruum the bi- selinite is only slightly soluble. The difficulty attending the prepara- tion of this salt is very great. Too much seleiiious acid must not be added to thc carbonate of potash or crystallization will never take place. When the liquid is made slightly acid the crystals are not more than two days in forming. Alcohol nearly always precipitates an oily liquid from the slightly acid aqueous solution which speedily howeever becomes crystalline. The crystals dried for eight days over suiphuric acid were analysed 0.894 grin. salt gave 8.351 , snlphate of potash leading to the forniula -KO SeO, +-130 SeO Theor!.Experiment. 2 eqs. of selenious acid . 118 66.272 1 , of potash . 48 28.402 28-05 1 , of water . 9 5.326 169 100-080 Biselenite of potash is analogous to the bisulphite of the sanic base KO SeO, -+ €10,SeO KO SeO, +1-10,SO,. On heating the biseleiiite iii a dry test-tube water first passes off and is followed by selenious acid. The whole mass then fwes to a red fluid which ultimately becomes colourless and on cooling solidifies into a fine crystalline mass soluble in water and pre- cipitable by alcohol. It is the neutral selenite of potash. ON THE SALTS OP SELENIOUS AClU. h most disagreeable odour of horseradish is evolved as the liquid reddens.The quadriselenite of potassa described by Berzelius-KO 4 SeO, or KO SeO, + 3 (HO SeO,) ? is not attainable in a fit state for analysis. This salt is styptic to the taste and when heated evolves most stifling funies. It is in a high degree deliquescent. SELENITES OF SODA. When carbonate of soda saturated with selenious acid is allowed to evaporate under a bell-jar the syrupy mass becomes filled with radiated crystals ; which will be subsequently described. The liquid gives a neutral salt on the addition of alcohol. This salt not being deliquescent is more easily obtained than the salt of potash. It was desiccated between folds of bibulous paper and then left over sulphuric acid for some days 0.400 grms. of salt gave 0.320 , sulphate of soda= 0.142 , soda agreeing with the formula NaO SeO,.Theory. Experiment. 1eq. selenious acid . . 56 63.63 1 , soda. . . 32 36-37 35.50 88 100~00 The above corresponds with the formuh for dry carbonate and sulphite of soda NaO CO NaO SO NaO SeO,. Selenite of soda heated in a test-tube gives off a mere trace of water thc salt fuses but does not suffer decomposition. Froin the aqueous solution I could not succeed in obtaining the neutral salt with water of crystallization. Biseleuite of soda forms acicular crystals. 0.2410 grins. oi salt gave 0.0251 , water. The annexed formula is deduced from the above NaO SeO, +' HO SeO + 2 aq DR. SHERIDAN MUSPRATT Represented in 100 parts Theory. Experiment.1 eq. of selenite of soda . 88 51 46 1 , , , , water . 65 38-02 2 eqs. , water-. 18 10.52 10.41 171 100.00 The biselenite does not suffer decomposition except at a very high temperature. On a sand-bath it parts only with its water of cfystallixation. At a red heat it fuses into a yellowish liquid water passing off with selenious acid; the neutral salt remains as a fine silvery-white crystalline mass. QUADRISELENITE OF SODA. I dissolved biselenite of soda in selenious acid and put aside the liquid to evaporate spontaneously. After some days needle-like crystals separated which were not very deliquescent When dried over sulphuric acid and analysed 0.862 grm. salt gave 0.241 , sulphate of soda = I-( 0.107 , soda. 0.804 grm. salt gave 11.{0.210 , sulphate of soda = 0.093 , soda. The preceding results agree closely with the followifig singular formula NaO SeO + 3 (HO SeO,) -+ aq. Theory. Experiment. I. 11. 4 eq. selenious acid . 224 76.712 1 , soda. . . 32 10-958 4 , water . 36 12-33 12.41 11.56 292 100.000 This salt fuses readily into a yellowish-red liquid evolving selenious acid and water while selenite and traces of selenate of soda remain. SELENITES OF AMMONIA. These salts are extremely difficult to prepare. I could not obtain a selenite of ammonia from an aqueous solution in a fit state for analysis ON THE SALTS OF SELENIOUS ACID. After a number of vain attempts alcohol was resorted to. SeIenious acid dissolved in alcohol and treated with ammoniacal gas afforded magnificent shining crystals which however were deliquescent.This salt is also obtained by dissolving selenious acid in strong aqueous ammonia and precipitating by alcohol. When a drop of strong ammonia is addcd to crystallized selenious acid combination imme- diately takes place great heat is evolved and particles of selenium some times separate . Selenite of ammonia is strongly alkaline to the taste and smells slightly of ammonia. It is very soluble in water-perfectly insoluble in ether 0.2505 grm. salt gave 0.25050 0.3100 , platinum = 0.31000 0*08141 , oxide of ammonium 0-08141 agreeing with the formula NH,O SeO,. Theory. Found. 1 eq. selenious acid . . 56 68.30 1 , oxide of ammoniuni 26 31.70 32-49 82 100.00 Selenite of ammonia hcated in a dry test-tubc gives off first water and ammonia then water and nitrogen while an acid salt condenses in the upper part of the tube; lastly large quantities of selenium sublime.The decomposition is represented in its several stages by the annexed equation. 5 (NH,O SeO,) = HO + 2 NH,O + 7 HO + 2 N +NH,O.2 Se-0, + 3 Se. Biselenite of ammonia does not deliquesce it is composed ac-cording to Berzelius as follows :-NH,O 2 SeO,. Its formula is probably NH,O SeO + HO SeO,? Quadriselenite of ammonia is not crystallizable. SELENITES OF BARYTA. Selenious acid produces no precipitate with solutions of baryta. By this reaction it is at once distinguished froni sulphurous acid. When neutral selenite of potash is added to nitrate of baryta decomposition takes place selenite of baryta is deposited in fine shinhg ~IUII~OSC crystals which are solulh in selenious nitric and hydroch!oric acids.From the acid solution the baryta is imme-diately precipitated by sulphuric acid. 0.308 grm. salt gave 0 271 , sulphate of baryta = 0.177 , baryta. Numbers agreeing with the formula Ba0 SeO Centesimally represented Theory. Berzelius. Experiment. 1 equiv. selenious acid . 56 42.42 42-07 -1 , barytes . . . 76 57.58 57.93 57.46 132 100*00 100.00 Biselenite of baryta is obtained by expelling the carbonic acid €rom the carbonate of baryta with seleiiious acid and allowing the liquid to evaporate spontaneously. It is with difficulty dissolved in water.Ammonia when added to it .precipitates the neutral salt. At a high temperature the biselenite evolves water and white fumes of selenious acid. SELENITES OF STRONTIA. These salts are obtained in a similar manner to those of baryta. Selenite of strontia is a white insoluble powder. It does not contain water. The following is its formula SrO SeO,. Biselenite of strontia does not crystallize. Its behaviour when heated corresponds to the acid salt of baryta. It is slightly soluble in water. SELENITES OF LIME. Carbonate of lime with selenious acid yields gritty crystals of selenite of lime. Berzelius has remarked the singular effect of this salt upon glass. At a red heat the tube is sometimes eaten through. A most remarltable characteristic of this ad a few other of thc salts of sclenious acid.Formula-CaO SeO The selenite of lime dissolves in selenious acid giving a biselenite which is very persistent in the air. ON TIIE SALTS OF SELESIOUS ACID. 61 When all the carbonic acid is e.ipellcd from carbonate of magnesia by selenious acid there reiliains a heavy neutral crystalline salt which dissolves in boiling wter and crystallizes from it in Aombic prisms. Selenite of magnesia heated over the lamp gives off only its water of crystallization. It fuses at a red heat in a glass tube corroding and passing through it like the selenite of lime. 0.209 grm. of salt strongly heated gave 0.056 , ,)water. Foxnula-MgO SeO 4-3 aq. Theory. Experiment. I 1 eq.Selenious acid . . 56 54.36 1 , Magnesia . . 20 19-42 -3 , Water . . 27 26.22 26.79 103 100.00 This salt is isoznoryhous with the sulphite and carbonate of the same base MgO SeO + 3 aq. MgO SO + 3 aq. 31g.0 CO + 3 aq. Selenite of magnesia dissolves in selenious acid yielding a biselenite precipitable in an unctuous state by alcohol. It is cxtreiiiely deliquescent. SELENITES 01' ALUhIINA. Alum is not precipitated by selenious acid. A selenite of an alkali however precipitates a selenite of alumina. Great care must be taken that the precipitant is nentral. Selenite of alumina is amorphous. When heated it gives off water and lastly all its acid. 0.197 grm. of dry salt gave 0.150 , selenious acid aiicl 0.046 , alumina.Theory. Esperiment. 3 eqs. Selenious acid . . 168 7'6.36 76-14 1 , Alumina . 52 23.64 23.36 Loss . . --50 220 I100.00 lOO*OQ 62 DR SHERIDAN MUSPRATT I also determined the water in the salt dried over sulphuric acid. 0.112 grm. of salt gave 0.012 , , water. Centesimally represented Theory. Experiment. 3 eqs. Seleiiious acid . . . 168 68-01 -1 , Alumina . 52 21-17 -3 , Water . 17 10.82 10.71 247 100*00 Formula-Al 0, 3 SeO + 3 aq. The composition of the selenite of alumina is greatly different from the sulphite as represented by the formula Al 0, SO + 4 aq. Biselenite of alumina is obtained when the above salt is dissolved in selenious acid. It is transparent and gummy to the feel. According to Berzelius it contains six equivalents of acid.Al 0, 6 SeO In all probability its composition is the following Al 0, 3 SeO + 3 (I10 SeO,) ? SELENITES OF GLUCINA. This selenite is in every way analogous to that of alumina the biselenite is extremely soluble and does not crystallize. SELENITE OF CHROIUIUM. This salt is obtained by decomposing the chloride of chromium by selenite of ammonia. It is a fine green amorphous powder. 0.3006 grm. salt gave 0.0980 , oxide of chromium. Formula-Cr 0, 3 SeO Theory. Experiment. 3 eqa. Selenious acid . . 168 67-74 -1 , Oxide of chromium . 80 32-26 32.60 248 100.00 Selenite of chromium dissolves in selenious acid giving on evapora-tion a green varnish. ON THE SALTS OF SELENIOUS ACID. SELENITES OF IRON.Metallic iron is not dissolved by selenious acid. Selenium is deposited on its surface in red flakes. Selenite of iron precipitates as a white powder from a mixture of an alkaline selenite and sulphate of iron. It becomes darker on exposure to the air and after some time partakes of a yellow colour owing to the forination of some sesquioxide. When the white precipitate is dissolved in hydrochloric acid a portion of selenium separates and sesquichloride of iron with selenious acid remain in solution. 4 (FeO SeO,) + 6 HC1 = Se + 2 (Fe Cl,,) + 6 HO + 3 SeO,. Biselenite of iron is formed by dissolving the selenite in selenious acid. When the liquid is boiled a brown powder separates con-taining selenite of the sesquioxide of iron with selenium.Selenite of the sesquioxide of iron falls as a white powder when selenite of ammonia is added to sesquichloride of iron. It is yellowish when dry and loses water in the heat becoming darker and as the temperature augments all its acid volatilizes 0.1015 grm. salt gave 0.0720 , selenious acid and water which agrees sufficiently with the formula Fe 0, 3 SeO + 4 aq. Calculated on 100 parts Theory. Experiment 1 eq. Sesquioxide of iron 80 28.16 -3 9 Selenious acid . . 168 59.15 4 , Water . * 36 l2*69{ 70'94 284 100.00 According to Berzelius the bisalt is formed when iron is dissolved in a hot mixture of nitric and selenious acids. The salt is deposited on cooling in green plates which contain water of crystallization. They are not soluble in water but dissolve readily in hydrochloric acid imparting a yellowish colour The formula for the salt is Fe 0,,3 SeO + 3 (HO SeO,) ? A basic salt is obtained when either of the two preceding salts is d-igested in ammonia the formula for which is 2 Fe 0,,3 ScO,.DR. SHERIDAN MUSPRITT SELENITES OF XIAPJC.lPJESE. I dissolved carbonate of manganese in selenious acid and obtaind a white gritty powder which readily fused to a dark liquid in a glass tube corroding it more even than the magnesia-salt. Sclenious acid sublimed and sesquioxide of manganesc with some selenium remained 05?00grm. salt fused with nitrate of potash gave 0.250 gri. selenate of baryta = 0.100 grm. sclenions acid. The formula is thereforc MnO SeO + 2 aq.Represented in 100 parts. Theory. Experiment. 1eq. selenious acid . . . 56 5090 5040 1 , oxide of manganese . 36 32.73 -2 , water . . . . . 18 16.37 -110 100~00 -This salt agrees in composition with the carbonate and sulphite of manganese MnO SeO + 2 aq. MnO CO + 2 aq. MnO SO + 2 aq. Selenite of mangancse is insoluble in water it forms a colourless solution in cold and a pink solution in hot hydrochloric acid TVith selenious acid it yields a soluble biselcnite. SELEXITES OF ArICKEL. The neutral salt falls as a greenish powder when selenite of potassa is added to sulphate of nickel. In its dry state the salt is white. Dried over sulphuric acid 0.207 grin. salt gave 0.019 , water. Numbers corresponding to the formula NiO SeO + aq.Calculated on 100 parts. Theory. Experiment. 1eq. selenious acid . . 56 54.36 -1 , oxide of nickel . . 38 36.89 7 1 , water . . . . . 9 8.75 9.1'7 103 100*00 ON THE SALTS OF SELENIOUS ACID Selenite of nickel dissolves in selenious acid with a greenish colour. The liquid on evaporation yields a gummy acid salt. SELENITES OF COBALT. The neutral salt procured by double decomposition is an insoluble rose-coloured powder. In all probability its composition is similar to the nickel compound. Carbonate of cobalt dissolves in selenious acid with a fine pink colour. The liquid on evaporation yields a magnificent transparent violet-coloured gum-an acid salt. This resinous substance when heated on a sand-bath g-ives off selenious acid which condenses on the sides ol the vessel in beautiful white needles.. SELENITES OF ZINC. Selenious acid does not precipitate salts of zinc; in combination with an alkali however it gives when added to sulphate of zinc white crystalline grains of selenite of zinc. When this salt is heated it evolves water but as the temperature augments the salt fuses to a yellow liquid which on cooling presents a fine crystalline striated appearance. At a white heat the niasx gives off selenious acid leaving a basic salt 0,0522 gun. salt gave 0*0087 , water. From which the following formula is deduced ZnO SeO + 2 aq. Represented in 100 parts Theory. Experiment. 1 eq. selenious acid . . 56 49.12 -1 , oxide of zinc .. . 40 35-08 -2 , water . . . . . 18 15.80 16.66 114 100*00 This salt corresponds to the sulphite of zinc ZnO SeO + 2 aq. ZnO SO + 2 aq. Selenite of zinc dissolves in selenious acid yielding an uncrystalli-zable biselenite. SELENITES OF CADXIUM. Selenious acid does not precipitate salts of cadmiurn. Selenite of ammonia gives with chloride of cadmium a white argillaceous looking TOL. II.-NO. Y* I? DR. SHERIDAN MWSPRATT precipitate. This becomes orange on exposure to the air. Selenite of cadmium contains no water It is soluble in selenious acid When heated in a test-tube it gives a sublimate of a yellowish-red colour. SELENITES OF COPPER. When biselenite of ammonia is added to a hot solution of sulphate of copper a dirty greenish-yellow precipitate falls which after some time becomes a fine bluish-green crystalline salt This compound dried over sulphnric acid acquires a beautiful bright blue colour.0.5260 grm. salt gave 0,2133 , oxide of copper. 0.0526 , salt gave 0-0018 , water and 0-0534grm. salt gave 11' { 0.0017 , water. The above results agree very closely with the formula 3 (CuO SeO,) + aq. Centesimally represented Theory. Experimernt. r I. 11. 3 eq. selenious acid . . . 168 56.56 -3 , oxide of copper . 120 40.40 40.55 -1 , water . . . 9 3-04 3.42 3.18 -7-297 100.00 This aalt does not dissolve in aqueous selenious acid. At a high tem- perature it first becomes brown lastly black parting with all its acid. A green basic selenite of copper is formed when selenite of ammonia is added to sulphate of copper.It is insoluble in water but dis- solves in ammonia. Freshly precipitated suboxide of copper combines with selenious acid producing a whitiah salt. The formula for which is Cu 0 SeO + aq.? SELENITEB OF LEAD. Selenious acid gives a white curdy precipitate with acetate of lead which is slightly soluble in water. The precipitate contains no water. It is with difficulty decomposed by sulphuric acid. When heated ON THE SALTS OF SELENIOUS ACID. very strongly it fuses into a yellowish fluid selenious acid sublimes and a basic salt remains. The formula for this salt is PbO SeO,. SELENITE OF SILVER. Berzelius analysed the selenite of silver.It is thrown down in the form of a white powder on the addition of aqueous selenious acid to nitrate of silver; it is fusible and at a red heat loses its acid and all its oxygen leaving metallic silver. When perfectly dry it is not blackened on exposure to light. It is slightly dissolved by cold more by boiling water is easily soluble in hot nitric acid from which it crystallizes in needles. The salt is obtained perfectly pure in this way. The formula for the salt is ,4gO Se02. SELENITES OF MERCURY. The selenite of the suboxide of mercury is obtained by adding selenious acid to a solution of subnitrate of mercury; also by double decomposition. It is a white powder insoluble in water. Heated in a tube it blackens water is liberated and a yellow powder sublimes.When the latter is heated it fuses into beautiful red globules which become of an orange colour on cooling ; in fact a series of cameleon- like changes occur with this salt. As the tube gradually cools splendent golden yellow crystals become visible. Caustic potash takes the selenious acid from the selenite. It dissolves in hydro-chloric acid giving chloride of mercury water selenious acid and selenium. 2 (Hg 0,SeO,) + 4HC1 = 4 (Hg Cl) + 4 HO + SeO + Se. Selenite of the protoxide of mercury is a white insoluble powder. The bisalt according to Berzelius is obtained by digesting the oxide of mercury for a long time in selenious acid. On filtering and eva- porating the filtrate prismatic crystals are deposited containing a large quantity of water.The salt fuses easily in its water of crystallization; as the heat is increased the selenite sublimes unchanged. Sulphurous acid preci- pitates from the selenite a mixture of sulphate of mercury and selenium 2 (HgO 2 SeO,) + 9 SO = Hg2 0 SO + 8 SO -i-Se. F2 $R. SHERIDAN MUSPRATT SELENITE OF LITHfA. This salt is obtained by double decomposition. It is deliquescent. When heated it fuses to a yellow liquid and on cooling solidifies into an opaque crystalline mass resembling mother-of-pearl. Selenite of lithia is soluble in selenious acid. SELENITE OF PTTHIA. Berzelius obtained the above as a white argillaceous precipitate which was insoluble in selenious acid. When dry it is a white amorphous powder which at first gives off water when heated and then acid.SELENITES OF CERIUill. Selenite of the protoxide of cerium is a white powder insoluble in water. A biselenite of the same oxide is obtained by dissolving the former in selenious acid. Selenite of the sesquioxide of cerium is a citron-yellow powder easily parting with its acid The biselenite is obtained by dissolving the above in selenious acid. When evapo-rated on a water-bath it leaves a yellow gummy mass which when heated loses water and becomes opaque and crystalline. It is soluble in water. SELENITES OF ZIRCONIA. The neutral salt is a white insoluble powder obtained by double decomposition. It loses its acid when heated and is soluble in selenious acid yielding an acid salt. SELENITES OF URANIUM.Selenite of uranium is a citron-yellow powder that gives off acid when strongly heated leaving a lower oxide; the bisalt yields on evaporation an opaque gum behaving like the selenite of the sesqui- oxide of cerium. The formula for this salt is U O, 3 SeO,. SELENITE OF ‘FIN. This salt is a white insoluble powder. It is soluble in hydrochloric acid from which solution it is reprecipitated by water. Heated it evolves first water selenious acid then sublimes and pure oxide of tin remains. The formula for the +y salt is SnOz 2 SeO ON THE SALTS OF SELENIOUS ACID. I have now described thc various compounds of this interest-ing acid. The difficulty of preparing the salts can only be known to the experimenter. Spontaneous evaporation or double decom- position is the best way to obtain the desired end.Alcohol can seldom be eniployed as a precipitant for it generally separates an oily liquid which becomes crystalline only in rare instances. The determination of selenious acid is very difficult ; fusion with nitrate of potash is the first step to convert the selenious into selenic acid which latter can then be precipitated by nitrate of baryta; selenate of baryta must not be burned in the filter as reduction readily takes place. To prevent loss when the selenate of baryta is perfectly dry it should be scraped from the filter into a weighed crucible and the filter burned over it. The selenites seldom correspond with the sulphites or carbonates; where such is the case the analogy has been noticed.The great stability of selenious acid has been previously discussed. Its salts when not deliquescent are most persistent. I shall close this memoir with a table of all the salts of selenious acid. Selenite of potash KO SeO Biselenite of potash . KO SeO,+ HO SeO Quadriselenite of potash . KO SeO +,3(HO SeO,) ? Selenite of soda . . NaO SeO Biselenite of soda . . NaO SeO + HO SeO + 2 aq. Quadriselenite of soda . NaO SeO,+ 3(HO SeO,) + aq. Selenite of ammonia . NH 0 SeO Biselenite of ammonia . NH 0 SeO,+HO SeO,? Selenite of baryta . . BaO SeO , , strontia . SrO SeO , , lime . . CaO SeO Biselenite of lime . . CaO SeO,+HO SeO ? Selenite of magnesia . MgO SeO + 3 aq. , , alumina . . Al 0, 3 SeO + 3 aq. Biselenit,eof alumina .Al 0, 3 ScO + 3 (HO SeO,)? Selenite of glucina . G1 0, 3 SeO -1-3 aq. ? , , chromium . Cr 0, 3 SOe . FeO SeO, , > Iron Biselenite of iron . . FeO SeO -l-HO SeO,? Selenite of the sesquioxide of iron . Fe 0, 3 SeO -I-4 as. Sesquiselenite of the sesquioxide of iron 2 Fe 0, 3 SeO Biselenite of the sesquioxide of iron . Fe 0, 3 SeO + 3 (HO SeO,)? Selenite of manganese MnO Se 0+ 2 aq. MR THORNTON Selenite of nickel . , , cobalt . , ? zinc , ) cadmium. . . , J copper . , , the suboxide of copper 3 , lead . , silver . . t , , the suboxide of mercury , , the oxide of mercury Biselenite of the oxide of mercury Selenite of lithia . , , yttria . , , the oxide of cerium .Biselenite of the oxide of cerium. J. IIERAPATH . NiO SeO + aq. . COO SeO + aq.? . ZnO SeO + 2aq. . CdO SeO . 3 (CuO SeO,) + aq. . Cu,O SeO + aq. ? . PbO SeO Ago SeO . Hg 0 SeO . HgO SeO . HgO SeO,’+ HQ SeO ? . LiO SeO . YO SeO . CeO SeO,? . CeO SeO,+ HO SeO,? Selenite of the sesquioxide of cerium. Ce 0, 3SeO ? Biselenite of the sesquioxide of cerium. Ce 0, 3SeO + 3(HO,SeO,)? Selenite of zirconia . Zr 0, 3 ScO , , uranium . U 0, 3 SeO 9 19 tin I * . SnO, 2Se0 All the preceding salts heated on charcoal before the blow-pipe impart a magnificent blue colour to the flame emitting the unmis-takeable and offensive smell of foul horse-radish. That many of them were obtained in definite crystals is due in a measure to the extreme coldness of the weather.It is valuable and interesting to ascertain the composition of the salts of some of those acids having ous for their termination. I purpose shortly communicating to the Society a paper on the Tellurites.