49 GRAHAM Esq. F.li.S. &. ( Was cornmenccd.) M r Arrott O?L a Class of Double Sulphates. January 1 1844.-'l'he President in the Chair. Mr. Warington presented Specimens of Chloride of Antimony a:id of Bichloride of Mercury in Crystals to the Society's Museum. William Lucas Esq. James P. Joule Esq. and Charles J. Hodg- son Esq. were elected Members. The following communications were then read :- On the Iklcat diseqaged irc Combinations. By THOMAS XCIV. On CJ Class of Double Sulphafes corttaining Soda nnd a ikfagnesian Oxide. By A. K. ARROTT Esq. W H E N a mixed solution of sulphate of soda. and any of the magnesian sulphotes is allowed to crystallize by spontaneous evaporation these salts always separate from their 50 r i ... ... 4 HO 4HO 4HO 2 HO Mr.Arrott on a Class of Double Sdphates. solution apart and in their ordinary form no double salt being produced. I find however that if the solution be kept at a temperature exceeding 100’ I?. the temperature at which anhydrous sul- phate of soda begins to be deposited a double salt is formed and this is true of all the magnesian sulphates. The double salts may generally be procured in well-defined crystals ex- cept that of copper which is usually deposited as a crystalline crust. One member of this class of double sulphates namely the sulphate of magnesia and soda was obtained by Dr. Murray in the manufacture of sulphate of magnesia from sea water being produced accidentally during the evaporation of the liquor; but he seems not to have been aware of the circum- stances of its formation.Several soda salts of the same class were also obtained by Mr. Graham by a process which he has described namely by mixing strong solutions of bisulpliate of soda and the mag- nesian sulphate in atcmic proportions; the double salt sepa- rated by crystallization in the course of a few days at the or- tliiiary temperature. The reason why no double salt of soda is formed at low temperatures seems to be the affinity of sul- p h t e of soda for water and the consequent formation of a hydrated sulphate of that base which cannot-enter into such combinations. I h i s interference is however prevented by the use of a high temperature at which as is well known sulphate of soda is deposited from its solution in the anhydrous condition and probably therefore exists dissolved in that state.The method which succeeds best is to dissolve the salts to- gether ill equivalent quantities and to evaporate at n tempe- rature of 130”. In this way I have formed the double salts of soda with magnesia zinc iron copper and manganese. The quantity of water contained in 100 parts of these salts was- Experiment. Theory. Siilphate of niagiiesia and soda 21-68 21.38 19.15 19-69 10.63 ... zinc ... iron ... copper ... . . . manganese 19*’iG 19.86 11.00 11.09 10*89 2 HO which gives 4atonis in the magnesia zinc and iron salts and 2 in those of manganese and copper the per-ceritage of water observed being in all cases rather above the atomic quantity from water mechanically included; double salts being as is Mr.Graham on the Heat disengaged in Combinations. 51 well known remarkable for the quantity of hygrometric water they retain. The salt of magnesia is generally said on the authority of Dr. Murray to contain 6 atonis of water but I have never found it to contain more than 4. These salts are persistent ir air and may be dried at 212' without losing their transparency ; the salts of manganese and magnesia decrepitate strongly when heated. After the loss of their water these salts are all fusible at a low red heat arid undergo that change without decomposition. When the double salt is dissolved in water and the solu- tion allowed to evaporate spontaneously its component salts always crystallize apart the dorible salt heing entirely de- coniposed ; this often happens also with 1 bisulphate of soda.In consequence of this effect of water the solubility at a low temperature ccdd not be observed. When a solntion of the copper salt is boiled a subsalt is precipitated resembling the subsalt of copper and potash formed under similar circumstances. I t is of a pale green colour loses nothing by drying at Z1Z0 but loses weight and becomes much deeper in colour when ignited; it therefore contains water besides an excess of oxide of copper. M r Arrott O?L a Class of Double Sulphates. 49 January 1 1844.-'l'he President in the Chair. Mr. Warington presented Specimens of Chloride of Antimony a:id William Lucas Esq. James P.Joule Esq. and Charles J. Hodg-The following communications were then read :-On the Iklcat diseqaged irc Combinations. By THOMAS GRAHAM Esq. F.li.S. &. ( Was cornmenccd.) XCIV. On CJ Class of Double Sulphafes corttaining Soda nnd a ikfagnesian Oxide. By A. K. ARROTT Esq. W H E N a mixed solution of sulphate of soda. and any of the magnesian sulphotes is allowed to crystallize by spontaneous evaporation these salts always separate from their of Bichloride of Mercury in Crystals to the Society's Museum. son Esq. were elected Members 50 Mr. Arrott on a Class of Double Sdphates. solution apart and in their ordinary form no double salt being produced. I find however that if the solution be kept at a temperature exceeding 100’ I?. the temperature at which anhydrous sul-phate of soda begins to be deposited a double salt is formed, and this is true of all the magnesian sulphates.The double salts may generally be procured in well-defined crystals ex-cept that of copper which is usually deposited as a crystalline crust. One member of this class of double sulphates namely the sulphate of magnesia and soda was obtained by Dr. Murray in the manufacture of sulphate of magnesia from sea water, being produced accidentally during the evaporation of the liquor; but he seems not to have been aware of the circum-stances of its formation. Several soda salts of the same class were also obtained by Mr. Graham by a process which he has described namely, by mixing strong solutions of bisulpliate of soda and the mag-nesian sulphate in atcmic proportions; the double salt sepa-rated by crystallization in the course of a few days at the or-tliiiary temperature.The reason why no double salt of soda is formed at low temperatures seems to be the affinity of sul-p h t e of soda for water and the consequent formation of a hydrated sulphate of that base which cannot-enter into such combinations. I h i s interference is however prevented by the use of a high temperature at which as is well known sulphate of soda is deposited from its solution in the anhydrous condition and probably therefore exists dissolved in that state. The method which succeeds best is to dissolve the salts to-gether ill equivalent quantities and to evaporate at n tempe-rature of 130”. In this way I have formed the double salts of soda with magnesia zinc iron copper and manganese.The quantity of water contained in 100 parts of these salts was-Siilphate of niagiiesia and soda 21-68 21.38 4 HO ... zinc ... 19*’iG 19.15 4HO ... iron ... 19.86 19-69 4HO ... copper ... 11.00 10.63 2 HO . . . manganese 11.09 10*89 2 HO which gives 4atonis in the magnesia zinc and iron salts and 2 in those of manganese and copper the per-ceritage of water observed being in all cases rather above the atomic quantity, from water mechanically included; double salts being as is r i Experiment. Theory Mr. Graham on the Heat disengaged in Combinations. 51 well known remarkable for the quantity of hygrometric water they retain. The salt of magnesia is generally said on the authority of Dr.Murray to contain 6 atonis of water but I have never found it to contain more than 4. These salts are persistent ir air and may be dried at 212' without losing their transparency ; the salts of manganese and magnesia decrepitate strongly when heated. After the loss of their water these salts are all fusible at a low red heat arid undergo that change without decomposition. When the double salt is dissolved in water and the solu-tion allowed to evaporate spontaneously its component salts always crystallize apart the dorible salt heing entirely de-coniposed ; this often happens also with 1 bisulphate of soda. In consequence of this effect of water the solubility at a low temperature ccdd not be observed. When a solntion of the copper salt is boiled a subsalt is precipitated resembling the subsalt of copper and potash formed under similar circumstances. I t is of a pale green colour loses nothing by drying at Z1Z0 but loses weight and becomes much deeper in colour when ignited; it therefore contains water besides an excess of oxide of copper