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Magnesium-potassium sulfate

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   Magnesium-potassium sulfate   
Names: dipotassium-magnesium sulfate
magnesium-potassium Tutton's salt
magnesium-potassium schoenite
KMSH
KMgSH
Formula: K2Mg(SO4)2 (anhydrous)
K2Mg(SO4)2 · 6H2O (hexahydrate)
Molar mass: 294.623 g/mol (anhydrous)
402.712 g/mol (hexahydrate)
Density: 2.201 g/cm3 (tetrahydrate)
2.028 g/cm3 (hexahydrate)
Crystal system: monoclinic (hexahydrate, picromerite)
a=6.1335 Å, b=12.2484 Å, c=9.0954 Åα=90°, β=104.88°, γ=90°
monoclinic (tetrahydrate, leonite)
a=9.889 Å, b=9.539 Å, c=11.769 Åα=90°, β=95.31°, γ=90°
Shapes:
https://en.crystalls.info/w/uploads/media/d/d0/Truncated_deformed_oblique_hexagonal_prism.json
Truncated deformed oblique hexagonal prism
https://en.crystalls.info/w/uploads/media/9/9a/Truncated_deformed_hexagonal_prism.json
Truncated deformed hexagonal prism

Color: colorless
white
Decomposition point: 130 °C403.15 K <br />266 °F <br />725.67 °R <br /> (tetrahydrate)
47 °C320.15 K <br />116.6 °F <br />576.27 °R <br /> (hexahydrate)
Refractive index: 1.479 (tetrahydrate)
1.461 (hexahydrate)
Stability: stable (hexahydrate)
hygroscopic (anhydrous)
Hardness: strong
(2.5 on Moh's scale)
Toxicity: non-toxic

Description

Inorganic compound, double salt of transitional metal magnesium, alkaline metal potassium and inorganic sulfuric acid. From water solutions crystallizes as hexahydrate.

Minerals

Occurs in nature as picromerite, schonite and leonite minerals.

Where to buy

Can be bought in fertilizers store (as "K-Mag" fertilizer).

Precursors

Reaction between magnesium and potassium sulfates

Chemical equation:

K2SO4 + MgSO4 = K2Mg(SO4)2↓


For preparation of 100.00g of magnesium-potassium sulfate hexahydrate а 79.56g of magnesium sulfate heptahydrate and 43.27g of potassium sulfate is required.

Dissolve compounds in hot water apart and then mix solutions into one container with intense stirring. Cooling or evaporation of a solution will cause double salt crystallyzation. Filter precipitate and wash it wish small amount of ethanol or acetone, then filter the solution and use it for crystal growing.

You could observe that compounds ratio is not equimolar. The cause is that firstly crystallizes potassium sulfate which is slight soluble, then begins crystallization of double sulfate. If there are some excess of magnesium, double salt crystallizes immediately at solution cooling.

Reaction between potassium chloride or nitrate and magnesium sulfate

Chemical equation:

2MgSO4 + 2KCl = K2Mg(SO4)2↓ + MgCl2
2MgSO4 + 2KNO3 = K2Mg(SO4)2↓ + 2MgNO3


For preparation of 100.00g of magnesium-potassium sulfate hexahydrate а 37.02g of potassium chloride or 50.21g of potassium nitrate and 159.13g of magnesium sulfate heptahydrate is required.

Add to the flask with saturated potassium salt solution a magnesium sulfate solution with stirring. Cooling this mixture will cause forming a large amount of crystalline precipitateof potassium-magnesium sulfate. For purifying compound from unreacted compounds add large amount of cold ethanol or acetone to solution, salt will settle to the bottom in the form of fine crystals or powder. Filter precipitate and wash it with small amount of the same solvent, then filter the solution and use it for crystal growing.

Reaction between potassium sulfate and magnesium chloride

Chemical equation:

2K2SO4 + 2MgCl = K2Mg(SO4)2↓ + 2KCl


For preparation of 100.00g of magnesium-potassium sulfate hexahydrate а 86.54g of potassium sulfate is required.

Dissolve compounds in hot water apart and then mix solutions into one container with intense stirring. Cooling or evaporation of a solution will cause double salt crystallyzation. For purifying compound from unreacted compounds add large amount of cold ethanol or acetone to solution, salt will settle to the bottom in the form of fine crystals or powder. Filter precipitate and wash it with small amount of the same solvent, then filter the solution and use it for crystal growing.

Influence of impurities

Small addition (~10%) of Tutton's salts, like nickel-potassium sulfate, cobalt(II)-potassium sulfate, copper(II)-potassium sulfate or magnesium-potassium sulfate-chromate can be used to change color of crystals. Adding large amounts of those sales may change crystal shape. It is also possible to cover crystals with a layer of other Tutton's salts, by placing the crystals into s saturated solution of other salt, producing a crystal-in-crystal.

Influence of pH level

Addition of surfactants has a positive influence on crystal shape and transparency. For example, addition of soap containing sodium lauryl sulfate makes crystal transparent and sharp-edged.

Storage conditions

Keep in its original form or under several layers of varnish at average humidity and room temperature. Do not keep crystals near heaters.

Solubility

Temperatureg/100,00 g water
0°C273.15 K <br />32 °F <br />491.67 °R <br />14.1
20°C293.15 K <br />68 °F <br />527.67 °R <br />18.3
80°C353.15 K <br />176 °F <br />635.67 °R <br />43.8
Insoluble in ethanol, acetone and ethylene glycol.



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   Sulfates
Simple

Aluminum sulfate (Al2(SO4)3) • Ammonium sulfate ((NH4)2SO4) • Calcium sulfate (CaSO4) • Cadmium sulfate (CdSO4) • Cerium(III) sulfate (Ce2(SO4)3) • Cerium(IV) sulfate (Ce(SO4)2) • Chromium(III) sulfate (Cr2(SO4)3) • Cobalt(II) sulfate (CoSO4) • Copper(II) sulfate (CuSO4) • Gadolinium sulfate (Gd2(SO4)3) • Holmium sulfate (Ho2(SO4)3) • Hydrazine sulfate (N2H4 · H2SO4) • Iron(II) sulfate (FeSO4) • Iron(III) sulfate (Fe2(SO4)3) • Lanthanum sulfate (La2(SO4)3) • Lithium sulfate (Li2SO4) • Magnesium sulfate (MgSO4) • Manganese(II) sulfate (MnSO4) • Neodymium sulfate (Nd2(SO4)3) • Nickel sulfate (NiSO4) • Potassium sulfate (K2SO4) • Praseodymium(III) sulfate (Pr2(SO4)3) • Rubidium sulfate (Rb2SO4) • Sodium hydrosulfate (NaHSO4) • Sodium sulfate (Na2SO4) • Yttrium sulfate (Gd2(SO4)3) • Zinc sulfate (ZnSO4)

Alums

Aluminum-ammonium sulfate (NH4Al(SO4)2) • Aluminum-potassium sulfate (KAl(SO4)2) • Chromium(III)-ammonium sulfate (NH4Cr(SO4)2) • Chromium(III)-potassium sulfate (KCr(SO4)2) • Cobalt(III)-ammonium sulfate (NH4Co(SO4)2) • Indium(III)-potassium sulfate (KIn(SO4)2) • Iron(III)-ammonium sulfate (NH4Fe(SO4)2) • Iron(III)-potassium sulfate (KFe(SO4)2) • Manganese(III)-ammonium sulfate (NH4Mn(SO4)2) • Vanadium(III)-ammonium sulfate (NH4V(SO4)2)

Tutton's salts

Chromium(II)-ammonium sulfate ((NH4)2Cr(SO4)2) • Cobalt(II)-ammonium sulfate ((NH4)2Co(SO4)2) • Cobalt(II)-potassium sulfate (K2Co(SO4)2) • Copper(II)-ammonium sulfate ((NH4)2Cu(SO4)2) • Copper(II)-potassium sulfate (K2Cu(SO4)2) • Iron(II)-ammonium sulfate ((NH4)2Fe(SO4)2) • Iron(II)-potassium sulfate (K2Fe(SO4)2) • Magnesium-ammonium sulfate ((NH4)2Mg(SO4)2) • Magnesium-potassium sulfate (K2Mg(SO4)2) • Magnesium-potassium sulfate-chromate (K2CrO4 · MgSO4) • Manganese(II)-ammonium sulfate ((NH4)2Mn(SO4)2) • Manganese(II)-potassium sulfate (K2Mn(SO4)2) • Nickel-ammonium sulfate ((NH4)2Ni(SO4)2) • Nickel-potassium sulfate (K2Ni(SO4)2) • Vanadium(II)-ammonium sulfate ((NH4)2V(SO4)2) • Zinc-ammonium sulfate ((NH4)2Zn(SO4)2) • Zinc-potassium sulfate (K2Zn(SO4)2)

Double salts

Copper(II)-iron(II) sulfate ((Cu,Fe)SO4) • Iron(II)-magnesium sulfate ((Fe,Mg)SO4) • Lithium-potassium sulfate (KLiSO4) • Sodium-ammonium sulfate (NaNH4SO4) • Zinc-sodium sulfate (Na2Zn(SO4)2)

Adducts

Triglycine sulfate ((NH2CH2COOH)3 · H2SO4) • Glutamic acid sulfate (C5H9NO4 · H2SO4)

Complexes

Cerium(III) sulfocerate(IV) (Ce4[Ce(SO4)4]3) • Glycinecopper(II) sulfate ([Cu(NH2CH2COOH)]SO4) • Hexakarbamatzinc sulfate ([(CON2H4)6Zn]SO4) • Tetraamminecopper(II) sulfate ([Cu(NH3)4]SO4) • Tris(hydroxymethil)methanoaminecopper(II) sulfate ([Cu(NH2C(CH2OH)3)4]SO4)



   Potassium compounds
Salts

Potassium bromate (KBrO3) • Potassium bromide (KBr) • Potassium chlorate (KClO3) • Potassium chloride (KCl) • Potassium chromate (K2CrO4) • Potassium dihydrophosphate (KH2PO4) • Potassium dichromate (K2Cr2O7) • Potassium iodide (KI) • Potassium hydrofluoride (KHF2) • Potassium hydrophosphate (K2HPO4) • Potassium hydrogen phthalate (KC8H6O4) • Potassium metavanadate (KVO3) • Potassium nitrate (KNO3) • Potassium sulfate (K2SO4) • Potassium thiocyanate (KNCS)

Double salts

Aluminum-potassium sulfate (KAl(SO4)2) • Antimony(III)-potassium tartrate (K2Sb2(C4H2O6)2) • Chromium(III)-potassium sulfate (KCr(SO4)2) • Cobalt(II)-potassium sulfate (K2Co(SO4)2) • Copper(II)-potassium sulfate (K2Cu(SO4)2) • Indium(III)-potassium sulfate (KIn(SO4)2) • Iron(II)-potassium sulfate (K2Fe(SO4)2) • Iron(III)-potassium sulfate (KFe(SO4)2) • Lithium-potassium sulfate (KLiSO4) • Magnesium-potassium sulfate (K2Mg(SO4)2) • Magnesium-potassium sulfate-chromate (K2CrO4 · MgSO4) • Manganese(II)-potassium sulfate (K2Mn(SO4)2) • Nickel-potassium sulfate (K2Ni(SO4)2) • Potassium-sodium tartrate (KNaC4H4O6) • Vanadium(III)-ammonium sulfate (NH4V(SO4)2) • Zinc-potassium sulfate (K2Zn(SO4)2)

Complexes

Potassium dioxalatocuprate(II) (K2[Cu(C2O4)2]) • Potassium hexanitrocobaltate(III) (K3[Co(NO2)6]) • Potassium hexachlororhodiate(III) (K3[RhCl6]) • Potassium hexacyanocobaltate(III) (K3[Co(CN)6]) • Potassium hexacyanoferrate(II) (K4[Fe(CN)6]) • Tripotassium-sodium hexacyanoferrate(II) (K3Na[Fe(CN)6]) • Potassium hexacyanoferrate(III) (K3[Fe(CN)6]) • Potassium hexacyanochromate(III) (K3[Co(CN)6]) • Potassium tetraiodobismuthate (К[BiI4]) • Potassium tetraiodomercurate(II) (K2[HgI4]) • Potassium trioxalatoaluminate (K3[Al(C2O4)3]) • Potassium trioxalatocobaltate(III) (K3[Co(C2O4)3]) Potassium trioxalatoferrate(III) (K3[Fe(C2O4)3]) • Potassium-sodium trioxalatoferrate(III) (K5Na[Fe(C2O4)3]2) • Dipotassium-sodium trioxalatoferrate(III) (K2Na[Fe(C2O4)3]) • Potassium trioxalatochromate(III) (K3[Cr(C2O4)3])


   Magnesium compounds
Salts

Magnesium hydrocarbonate (Mg(HCO3)2) • Magnesium sulfamate (Mg(NH2SO3)2) • Magnesium sulfate (MgSO4)

Double salts

Iron(II)-magnesium sulfate ((Fe,Mg)SO4) • Magnesium-ammonium sulfate ((NH4)2MgSO4) • Magnesium-potassium sulfate (K2MgSO4) • Magnesium-potassium sulfate-chromate (K2CrO4 · MgSO4)

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