Magnesium-potassium sulfate

From Crystal growing

<amp/>


   Magnesium-potassium sulfate   
Names: dipotassium-magnesium sulfate
magnesium сернокислый potassiumный
magnesium-potassium Tutton's salt
magnesium-potassium schoenite
NMSH

Formula: K2Mg(SO4)2 (anhydrous)
K2Mg(SO4)2 · 6H2O (hexahydrate)
SMILES: [O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[Mg+2].[K+].[K+]
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=9.066 Å, b=12.254 Å, c=6.128 Åα=90°, β=104.78°, γ=90°
monoclinic (tetrahydrate, leonite)
a=11.769 Å, b=9.539 Å, c=9.889 Åα=90°, β=95.31°, γ=90°
Shapes:
https://en.crystalls.info/w/uploads/media/Truncated_deformed_oblique_hexagonal_prism.json
https://en.crystalls.info/w/uploads/media/Truncated_deformed_hexagonal_prism.json

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

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. Freezing 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.

Storage conditions

Store in its original form or under several layers of varnish at average humidity and room temperature. Do not store in matchboxes or cotton wool and do not heat.

Solubility

Temperatureгр/100,00 гр water
0°C273.15 K <br />32 °F <br />491.67 °R <br />14.1
10°C283.15 K <br />50 °F <br />509.67 °R <br />~16.2
15°C288.15 K <br />59 °F <br />518.67 °R <br />~17.3
20°C293.15 K <br />68 °F <br />527.67 °R <br />18.3
25°C298.15 K <br />77 °F <br />536.67 °R <br />~20.4
30°C303.15 K <br />86 °F <br />545.67 °R <br />~22.5
40°C313.15 K <br />104 °F <br />563.67 °R <br />~26.8
50°C323.15 K <br />122 °F <br />581.67 °R <br />~31.1
60°C333.15 K <br />140 °F <br />599.67 °R <br />~35.3
70°C343.15 K <br />158 °F <br />617.67 °R <br />~39.6
80°C353.15 K <br />176 °F <br />635.67 °R <br />43.8
Insoluble in ethanol, acetone and ethylene glycol.


Gallery


Video


Sources


Navigation