The storm glass

I’m going to introduce you to the world of meteorology,

From 1834 to 1836, Charles Darwin made his expedition aboard the HMS Beagle, commanded by Admiral Fitzroy (1805-1865). The Beagle carried several barometers and chronometers. Fitzroy also carried one barometer which he had designed and built, the storm glass.

The storm glass was used for weather forecasting. It consists of a glass tube, hermetically sealed, filled with a transparent liquid. Observing it, one could guess the weather in the following days. If the glass is clear, the weather likely will be clear and sunny; if the glass is milky, the weather will be cloudy; if the glass is cloudy and it has little dots, there will be storms or it will snow.

The functioning of this kind of barometer is not fully understood. On the one hand, solubility of the mixture could be affected by temperature changes, and storms or weather changes could be detected by changes in the atmospheric pressure. On the other hand, there have been several experiments with different conditions of temperature and pressure, always with the same results; and the tube is made from glass and sealed, so pressure changes are indifferent to it. Almost two hundred years after its creation, we don’t know how does it works. Some scientist suggest that that the electrical effects that generate  storms and involve the appearing of snowflakes, also could interact with the storm glass in the same way as they do with clouds.

Of course you can buy one of these expensive nautical instruments, but you can build one of your own, and get the same results. The reader is advised to use proper care in handling the chemicals. All you need is:

• 2.5 g potassium nitrate  KNO_{3 (Strong oxidizer, toxic when inhaled and by skin contact)}
• 2.5 g ammonium chloride  NH₄Cl  (Very toxic when inhaled)
• 33 mL distilled water
• 40 mL ethanol  CH₃CH₂OH
• 10 g camphor  C₁₀H₁₆O   (Irritating when inhaled and by skin contact)

In order to prevent strong or explosive reactions, you have to follow the steps very carefully:

1. Dissolve the potassium nitrate in the water.
2. Dissolve the ammonium chloride in the water.
3. In another glass, dissolve the camphor in the ethanol.
4. Slowly, mix both solutions, adding the nitrate & ammonium solution to the ethanol solution.

You can find further information about how to interpret the storm glass

Finally, I hope you to enjoy your brand new nautical instrument. 

 

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