Alkaline earth metal hydroxides are solid white, deliquescent in air to water absorption. Among them, Ca(OH) 2 is a commonly used desiccant. The solubility of alkaline earth metal hydroxides in water is much smaller than that of alkali metal hydroxides. From the data in the table, the solubility of hydroxides increases from Be to Mg, and their alkalinity increases. Be(OH) 2 and Mg (OH) 2 are poorly soluble hydroxides. Be(OH) 2 is an amphoteric hydroxide, Mg (OH) 2 belongs to a medium strong base, and the rest belong to a strong base. Table 1  Some properties of alkaline earth metal hydroxides substance Be ( OH ) 2 Mg ( OH ) 2 Ca ( OH ) 2 Sr ( OH ) 2 Ba ( OH ) 2 nature colour White White White White White Melting point / K Dehydration decomposition Dehydration decomposition Dehydration decomposition Dehydration decomposition Dehydration decomposition Solubility in water / mol-dm -3 ( 293K ) 8×10 -1 S×10 -1 1. 8×10 -2 6. 7×10 -2 2×10 -1 Acidity and alkalinity Sexuality Medium alkali strong base strong base strong base  Flame color of alkali metal and some alkaline earth metals ion Li + Na - K + Rb + Cs + Ca 2+ Sr 2+ Ba 2+ Flame color red yellow purple Purple red Purple red Purple red Magenta Yellow green Wavelength / nm 670.8 589.6 404.7 629.8 459.3 616.2 707 553.6 The density of Mg(OH) 2 is 2.36 g/cm 3 , and it is dehydrated by heating to 623 K: Activated Alumina,Activated Alumina Balls,Alumina Desiccant,Alumina Adsorbent Ningbo Cijie Chemical Equipment Co., Ltd. , https://www.chemicaltower.com
Mg(OH) 2 ==== MgO + H 2 O
Mg(OH) 2 is easily soluble in acid or ammonium salt solution:
Mg(OH) 2 + 2HCl ==== MgCl 2 +2H 2 O
This reaction can be applied to analytical chemistry.
The reaction of milk of lime water and cheap, can be obtained Mg (OH) 2 precipitate, known as magnesia milk:
Mg 2+ + Ca(OH) 2 == Mg(OH) 2 + Ca 2+
A milky suspension of Mg(OH) 2 is used medicinally as an antacid and a laxative.
Brief introduction of magnesium hydroxide