Does the boiling point of ammonia hydroxide change with the ratio of water to ammonia?

My kids and I are designing a science experiment and we could use help with the ratio of water to ammonia in an ammonia hydroxide mixture.


A little bit of background:


Initial goal: To convert the ammonia hydroxide into gas through solar / ambient heat with enough pressure to inflate a balloon.


The how: We have a metal tank that is painted black. The balloon is wrapped around the outlet of the tank at the top of the tank. We put the ammonia hydroxide in the tank when cool outside, then wait for the day to warm (we live in the high desert) and ammonia to turn into vapor.


Initial tests will fill the balloon but does not generate enough pressure to expand the rubber/plastic to properly inflate it.


Our idea, and the genesis of this question, is that if we use a higher concentration of ammonia we will a) boil faster at lower temperatures and b) might generate more vapor and create pressure to inflate the balloon.


Apologize in advance if this question is incomplete. Happy to provide more information. And thanks for your help!




Your idea of increasing the ammonia concentration to increase the total vapor pressure over the solution is physically sound. For two-component mixtures, the total pressure will be a function of both solution composition and temperature. In the case of ammonia and water, since ammonia is the more volatile component (it is a gas at standard conditions) increasing its concentration will lead to a higher vapor pressure for the solution.


Although the data are over 100 years old, a paper by Perman (*J. Chem. Soc.*, **83**, 1168 (1903)) gives some relevant information. Below is a table with the vapor pressures he measured for ammonia solutions at various temperatures and ammonia concentrations. You should be able to calculate the pressure ratios you're interested in from these data.


[![enter image description here](https://i.stack.imgur.com/wRLua.png)](https://i.stack.imgur.com/wRLua.png)


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