Mr. Cameron on Vapour from Saline Water. £•17 



water boiled, tbe thermometer in the water indicated 221° 8', and the 

 one in the steam indicated 220° 5': at this point the mercurial gauge 

 indicated a rising along with the thermometer. 



The water was then removed, and replaced by saturated water, its 

 boiling point being 226°, when similar results followed as in the former 

 case. The apparent difference of heat in the steam and water, I think, 

 arises from the steam being more sensitive to cooling effects. 



It will be evident, from these experiments, that the water and steam 

 are nearly of the same temperature, and whatever the amount of satura- 

 tion may be, its vapour can only balance the atmosphere when the water 

 is at the boiling point. 



Tliis brings me to the point that has been called in question by many, 

 as they maintained that the vapour from saline water, at 212°, was equal 

 to the pressure of the atmosphere. 



From the above experiments, and the experiments which follow, I hope 

 you will be satisfied that such is not the case. 



This led me to examine the vapour from saline water, to ascertain 

 whether it did not contain a portion of salt. 



To the blow-off stop-cock was attached a glass tube, having a globe at 

 its end, which was immersed in water. The vapour fi-om saturated water 

 was then allowed to pass freely into the globe to be condensed. I then 

 removed it, and applied a few drops of nitrate of silver, when, at the 

 moment of contact, it showed the condensed vapour to contain salt. 

 This may be one of the causes why vapour, from saline water, requires a 

 greater amount of heat, compared to that from vapour from pure water, 

 as the salt contained in the vapour must occupy a certain amount of its 

 bulk, therefore its elastic force must be less in proportion to the extent 

 of saturation. It was from these deductions I was led to the construc- 

 tion of one of the scales on the salinometer, showing the decrease of the 

 elastic force in proportion to the amount of saturation. 



From deductions made from a few of the foregoing experiments, I was 

 led to the construction of the two other scales on the salinometer. 



In a former paper I stated it was necessary, that in proportion to the 

 extent of saturation, so must there be a proportionate increase of injection 

 water to the condenser, for the engine to work effectively. It is evident 

 (from tables which I have drawn up) that, in proportion to the extent of 

 saturation, there is a proportionate increase of heat and loss of elastic 

 force ; hence the necessity of care being taken to keep the water as free 

 as possible from increased saturation. On a previous evening I did not 

 refer to any other instrument used for finding the quantity of salt con- 

 tained in the water of marine boilers ; but I beg to take the liberty noAV 

 of referring to them. The scales of the different instruments I have seen 

 used for this purpose, have been constructed from experiments made with 

 salt dissolved in cold water, in different proportions, so that the one in 

 present use cannot give even an approximation, as the saturated point of 

 boiling water will be upwards of three pounds to the gallon, and that of 



