The 



con- 



of Water at High Temperatures. 129 



{£__ q^[ 6 

 ~JT~ f = ^> 



{y — t~} p 1 - k 



1— V = D = -, orvp = ~- —- 



nexion between them is that h ocp, or- oc-« 



r h p 



On the axis of temperature AH take AG=^ and AH = 7, reckon- 

 ing all temperatures t as well as ^ — 72? 

 7fromAthezeroof gaseous ten- 

 sion. Draw RH _L to AH, and 



set off H R = (7 — g) — . Join 



GRand draw RP || to axis. At 



a point L corresponding to a 



given temperature t = A L 



draw the _L L Q P, cutting 



G R in Q. We have P Q a A 8T I 



constant function of the density of the 



the temperature, and QL a constant function of the density 



of the saturated vapour in terms of the temperature. P R is 



(y — t), and P Q is (y—t) — = —=—; so that the inverse of P Q 



represents the proportionate increment of volume or decrement 

 of density for 1 degree. Again, we have GL= (t—g), and 



Q,L=(t— g)— ; and since - =P (the constant 504), we have 

 ~~ \t~9) Tu = *7vT > anc * smce the sixth power 



G 



liquid 



in terms of 



= -=- anc 



P F 



pF 504' 



QL 



is equal to density A, we have — — to represent the sixth 



504 



root of the density of the saturated vapour — taking the word 

 density to mean the quotient of the pressure or tension by the 

 temperature reckoned from the zero of gaseous tension (A). 



Suppose gr to represent the chart-line of another body, say 

 cyanogen, and p q I to be the vertical of t v If p q = V Q, then 

 the value of the proportionate increment of volume of cyanogen 

 at /j would be the same as the proportionate increment of water 

 at t, and so on ; if it is double or half, the proportionate incre- 

 ment is double or one-half. If q l=Q L, the gaseous density of 

 cyanogen vapour at t 1 is equal to the gaseous density of water 

 vapour at / ; that is to say, their absolute densities bear the same 

 ratio to each other as their vapours do when in (equilibria of 

 pressure and temperature at 15° separated from their liquids. 



Phil. Mag. S. 4. Vol. 26. No. 173. Aug. 1863. K 



