Table 1.

Saturated solutions of ammonium sulfate in water at several temperatures

Temp (°C)	Grams (NH4)2SO4 required to saturate 1000 g of H2O a,b	Grams (NH4)2SO4 added per liter of saturated solution c	Moles (NH4)2SO4 in 1000 g of H2O	Percentage by weight	Molarity of saturated (NH4)2SO4 solution	Apparent specific volume in saturated solution c	VG/1000 c
0	706.86	514.72	5.35	41.42	3.90	0.5262	0.271
10	730.53	525.05	5.53	42.22	3.97	0.5357	0.281
20	755.82	536.34	5.73	43.09	4.06	0.5414	0.290
25	766.80	541.24	5.82	43.47	4.10	0.5435	0.294
30	777.55	545.88	5.91	43.85	4.13	0.5458	0.298

^aNote that the volume changes upon addition of solid (NH₄)₂SO₄.

^b The degree of saturation is usually considered to be that which is calculated for the addition of a saturated solution without allowing for a volume change upon mixing. For example, 1 volume of water plus 1 volume of saturated (NH₄)₂SO₄ is considered to yield a solution that is 0.5 (50%) saturated. According to this convention, the volume (V) of saturated (NH₄)₂SO₄, which has to be added to 100 ml of solution of initial saturation S₁ to produce a final saturation S₂ is given by the equation: V=100(S₂-S₁)/(1-S₂), where S₁ and S₂ are expressed as fractions of the saturated solution. For example, if S₁=0.5 and S₂=0.7, then V=66.67 ml.

^c When preparing more concentrated solutions of (NH₄)₂SO₄, it is more economical and often more convenient to add the solid salt instead of a stock solution of saturated (NH₄)₂SO₄. The weight in grams, X, to be added to 100 ml of solution of saturation S₁ to yield a solution of saturation S₂ may be calculated as follows: X=0.1G(S₂-S₁)/(1-(VG/1000)S2), where G=grams of (NH₄)₂SO₄ in 1000 ml of saturated solution, and V=apparent specific volume of (NH₄)₂SO₄ in a saturated solution. Values of G, V, and VG/1000 at different temperatures are given in columns 3, 7, and 8, respectively. For example, if S₁ = 0.5 and S₂=0.7, at 0°C, G=514.72 and VG/1000=0.271, then X=20.2 g.