SODIUM CHLORIDE-BERTHOLLET'S IAWS 453 



density (4) aa 10,000, for solutions containing p per cent, of hydrogen 



chloride are 



p S* p S 



5 lu,242 25 11,266 



10 10,490 30 11,522 



15 10,744 35' 11,773 



20 11,001 40 11,997 



The formula =9,991-6- 4- 49-4 3/>+ 0-057 ty 2 , up to ^=5=25-26, vhich 

 answers to the hydrate HC1,6H 2 mentioned above, gives the specific 

 gravity. Above this percentage S = 9,785-1 + 65-lOjt? - 0'240/>* The 



At a pressure of 760 millimetres and temperature t, one hundred grams of water 

 dissolves 



t = 8 16 24 40 60 



Grams HC1 82'5 78'8 74'2 70'0 63'3 561 



Eoozeboom (1886) showed that at < solutions containing c grams of hydrogen chlo*iu 

 per 100 grama of water may (with the variation of the pressure p) be formed togethe* 

 with the crystallo-hydrate HC1,2H 2 O: 



* = -28-8 -21 -19 -18 -17-7 



c = 84-2 86-8 92-6 98'4 101'4 



p = 884 580 900 1,073 mm, 



The last combination. answers to the melted crystallo-hydrate HC1,2H 2 0, which splits up 

 at temperatures above 17'7, and at a constant atmospheric pressure when there are no 

 crystals-?- 



t = -24 -21 -18 -10 



c = 101-2 98-3 95-7 89'8 84'2 



From these data it is seen that the hydrate HC1,2H 2 can exist in a liquid state, which 

 is not the case for the hydrates of carbonic and sulphurous anhydrides, chlorine, &c. 



According to Marignac, the specific heat c of a solution HCl + mH 2 O (at about 80, 

 taking^ the specific heat of water =1) is given by the expression 



C(86'5 + w!8) 18m- 28-89 + 140/m- 268/m l 



if m be not less than 6'25. For example, for HC1 + 25H 2 0, C = 0'877. 



According to Thomsen's data, the amount of heat Q, expressed in thousands of caloriep, 

 evolved in the solution of 86:5 grams of gaseous hydrochloric acid in mH 2 or 18m grama 

 of water is equal to 



m = 2 4 10 50 400 



Q = 11-4 14-8 16-2 17-1 17'8 



In these quantities the latent heat of liquefaction is included, which must be taken 

 as 5-9 thousand calories per molecular quantity of hydrogen chloride. 



The researches of Scheffer (1888) on the rate of diffusion (in water) of solutions of 

 hydrochloric acid show that the coefficient of .diffusion k decreases with the amount of 

 water n, if the composition of the solution is HClnH 2 O at : 



n = 6 &9 9-8 U 27*1 129*5 



A = 2-81 2-08 1-86 1'67 1'62 1'39 



It also appears 'that strong solutions diffuse more rapidly into dilute solutions than 

 Into water. 



