Mr. Detmer on Bleachhg Salts. 11. On Bleaching Salts. By M. DETMER ESP. Read April 27 1841. ASHORT time ago a notice was published by M. Millon ’ on the Bleaching Salts of Chlorine in which a new view was offered of the constitution of these com ounds. They have for some time pastgenerally been consi 1pered as compounds or mixtures of a metallic chloride with a hypochlorite of a metallic oxide ; bleaching powder or the chloride of lime for instance as consisting of chloride of calcium and hypochlorite of lime in single equivalents the acid of the last salt contain-ing one atom of oxygen to one atom of chlorine. The reac- tion of chlorine upon lime supposed may be very simply stated two atoms of lime take up two of chlorine; one atom * Ann. de Chitn et de Phys.t. Ixiii. 118. .1. Zbid. t. Ixvi. 172. Mr. Dekmer on Rleacliiiig SaZfs. only of the lime is decomposed of which the calcium and oxygen respectively unite with an atom each of chlorine form- ing chloride of calcium and hypochlorous acid. The hypo- chlorous acid combines with the other atom of lime. Starting froin the composition of chlorochromic and chloro- sulphuric acids which are represented by Walter and Re- gnault as chromic and siilphuric acids in which the third pro- portion of oxygen is replaced by chlorine (Cr 0 + C1 and S 0,+ Cl) Millon supposes that the bleaching chlorides have a similar relation to the peroxides of their metals. The per- oxide of calcium being Ca O, or Ca O+ 0 bleaching pow- der is Ca O+ CI or the peroxide of calcium with chlorine substituted for its second proportion of oxygen.In support of this view Millon adduces observations of his own on the composition of the bleaching compounds of chlorine with dif- ferent metallic oxides such as oxides of lead and protoxide of iron as well as potash soda and lime in which the pro- portion of chlorine was found to vary but to correspond with the excess of oxygen above one equivalent in the peroxides of the same metals. In particular potash was found to absorb two equivalents of chlorine and soda only one the peroxide ofpotassium being K 0 + 2 0 while ttie peroxide of sodium is Na O+O. The attention of the author was particularly directed to ascertain the accuracy of the latter statement.A solution of carbonate of soda was charged with chlorine gas till it acquired a yellow colour and retained not a trace of carbonic acid. The solutiou was then briskly agitated with air by which the excess of free chlorine escaped. In analyzing the solution afterwards one portion of it was treated with a few drops of ammonia and the chlorine afterwards precipitated by nitrate of silver ; another portion was evaporated to dryness for the sodium which was obtained in the state of chloride of sodium. In four experiments the liquids charged with chlorine con- tained chlorine and sodium in the followiiig proportions in 100 parts :-Sodium.... .. 47-88 45.26 46.81 44.76 Chlorine. ... 52.12 54-74 53.1 9 55.24 while if the bleaching chloride of soda contained 1 eq.of chlorine to 1 eq. of soda its composition would be 1eq. sodium ......... 46-91 1 eq. chlorine. ...... 53.09 1oo*oo The results correspond as closely RS could be expected with this theoretical statement. There can be no doubt then that ttie chloride of soda contains one of ciilorine to one ot' Mr. Detmer on Bleachiq Salts. soda. I’his is the result reqriired by Alillon’s theory the peroxide of sodium containing according to him one of oxy-gen and one of soda; but it is equally consistent with Balard’s theory that the salt is R nlixture of single equivalentsof chlo- ride of sodium and hypochlorite of soda. To determine the quantity of chlorine which water dissolves a stream of the gas was sent through water at 59O for five hours.One hundred gramnies of water were found to take up 0.663 grainme of chlorine; or 200 cubic inches of water dissolved 207 cubic inches of gas. The chlorine was estimated by converting it into hydrochloric acid by the addition of a few drops of mi-monia slightly acidulating afterwards by nitric acid and pre- cipitating by nitrate of silver. A solution of‘ 2.58 cliloride of potassium in 38.96 water was found to dissolve less chlo- rine than pure water in the proportion of’180 to 257. Chlo-rine gas being allowed to stream through a solution of 9-245 grammes carbonate of potash in 96’495 grammes of water till saturation the solritioii lost all its carbonic acid aiid took up G.681 gramnies of chlorine. Here 1 eq. of potash =590 has taken up Gti6 chlorine which is very nearly 1$ eq..of chlorine = 663. But when the quantity of free chlorine in the liqiiiti is deducted the latter is found to ccmtain only 2-34equivalents of chlorine to 1 eq. of potash. In two other experinients in which the liquid was agitated with air after beirig saturated with chlorine to allow the excess of gas to escape there were found to 1 eq. of potash 1.44 and 1-49equivalents of chlorine. The carbonate of potash therefore without doubt takes up more than a single equivalent of chlorine. But the quantity of chlorine combined with the potash is still greatly short of two equivalents the proportioti 1-equireti by M. Millon’s theory ; the peroxide of potassiuni containing two oxygen to one potash or K 0,.The conclusioii therefore is inadmis- sible that tlie chloride of potash is analogous in constitution to the peroxide of potassium. It remains to account for the property which potash is found to possess of taking up niore chlorine than is necessary to convert it into chloride of potassium and hypochlorite of potash. On transmitting chlorine through carbonate of pot-ash a stage in the absorption is very observable at which the liquid becornes all at once of a yellow colour. This happens when what remains of the potash is entirely converted into bicarbonate of potash. The suddenness of the appearance of‘ the yellow colour appears to be due to a reaction of the car- bonic acid upon the hypochlorite of potash in solution by which hypochlorous acid is set free and tinges the liquid.By the continued application of chlorine to the liicarbonate of Mr. Iletiner ou BLeiichiiig Snlts. potash it is converted into a mixture of chlorideof potassium hypochlorite of potash and free hypochlorons acid. By the ultiinate action of the chlorine all the bicarbonate of potash is decomposed the carbonic acid entirely expelled and a por-tion of hypochlorous acid remains free in solution. This formation of free hypochlorous acid does not occur with carbonate of soda owing to the much weaker affinity which that base has for carbonic acid and its forming a much less stable hicarbonate than potash does. The free carbonic acid cannot therefore react upon the hypochlorite of soda and liberate hypochlorous acid as the free carbonic acid does upon the hypoclilorite of' potash.The same formation of free hypochlorous acid occurs in a more striking degree when chlorine is sent through a solution of acetate of potash ; that solution it is well known absorbs a large quantity of gas and acquires the strong yellow colour the odour and all the other properties of free hypochlorous acid. It is here evident that by the action of chlorine upon acetate of potash chloride of potassium is formed with the binacetate of potash free liypo- chlorous acid and the hypochlorite of'potash. If the large absorption of chlorine by carbonate of potash is due to car- bonic acid it follows that caustic potash should not absorb any excess of chlorine but that the property should be con- fined to the carbonate.Accordingly in two experiments the proportion of chlorine absorbed by caustic potash was found to be as nearly as possible a single equivalent. In one ex- periment 449'1 chlorine in the other 424.8 chloriiie were taken up instead of 442.6 chlorine by a single equivalent or 589-9 of potash. Caustic potash therefore dissolves no more chlorine than caustic soda. There appears therefore to be no reason to a\)andon the old theory that the bleaching solu-tions of chlorine in alkalies and alkaline earths cont:tiii a chlo-ride anti hypochlorite for these bleaching cornpouiitls certainly do not correspond with nietallic I,eroxides as has been lately rnain tained.