solution took place was _t_°, then it follows that at the temperature _t the co-efficient of solubility of the gas_ in 1 volume of the liquid will be equal to _m_/_n_ × 760/_h_. This formula is very clearly understood from the fact that the co-efficient of solubility of gases is that quantity measured at 0° and 760 mm., which is absorbed at a pressure of 760 mm. by one volume of a liquid. If _n_ cubic centimetres of water absorb _m_ cubic centimetres of a gas, then one cubic centimetre absorbs _m_/_n_. If _m_/_n_ c.c. of a gas are absorbed under a pressure of _h_ mm., then, according to the law of the variation of solubility of a gas with the pressure, there would he dissolved, under a pressure of 760 mm., a quantity varying in the same ratio to _m_/_n_ as 760 : _h_. In determining the residual volume of gas its moisture (note 1) must be taken into consideration. Below are given the number of grams of several substances saturating 100 grams of water--that is, their co-efficients of solubility by weight at three different temperatures:-- +----------------------------------------------+--------+---------+ | | | | | At 0° | At 20° | At 100° | +----------------------------------------------+--------+---------+ | {Oxygen, O_{2} 6/1000 | 4/1000 | -- | |Gases {Carbonic anhydride, CO_{2} 35/100 | 18/100 | -- | | {Ammonia, NH_{3} 90·0 | 51·8 | 7·3 | | {Phenol, C_{6}H_{6}O 4·9 | 5·2 | [oo] | |Liquids {Amyl alcohol, C_{5}H_{12}O 4·4 | 2·9 | -- | | {Sulphuric acid, H_{2}SO_{4} [oo] | [oo] | [oo] | | {Gypsum, CaSO_{4},2H_{2}O 1/5 | 1/4 | 1/5 | | {Alum, AlKS_{2}O_{8},12H_{2}O 3·3 | 15·4 | 357·5 | |Solids {Anhydrous sodium sulphate, 4·5 | 20 | 43 | | { Na_{2}SO_{4} | | | | {Common Salt, NaCl 35·7 | 36·0 | 39·7 | | {Nitre, KNO_{3} 13·3 | 31·7 | 246·0 | +----------------------------------------------+--------+---------+