Storm in a glass – NRC

Storm in a glass – NRC

Not all promotional gifts that the AW laboratory receives are equally harmless. Last week the upside-down test tube in the photo arrived, with an instruction leaflet that you disagree with. “If the glass breaks and one is exposed to the contents, seek medical attention immediately. In case of skin contact: wash immediately with soap and plenty of water for 15 minutes. Remove contaminated clothing and shoes.” It seemed best to immediately take the case to the recycling center.

But it wasn’t that bad. The glass cylinder appears to be a half-size replica of an instrument that was devised around 1770 to predict the weather and especially the wind strength. It’s a storm glass. There is nothing creepier than some camphor contained in alcohol of about 55 percent in which the salts potassium nitrate and ammonium chloride are also dissolved. Saltpeter and sal ammoniac, as they used to be called. You shouldn’t get too much camphor, that’s true, but otherwise you could knock back the storm glass like a stiff drink. Assuming you managed to break it open.


No one knows who invented storm glass. It is first mentioned in 1782, but would not have been there before 1765, otherwise it would have been in the Encyclopedia of Diderot and d’Alembert. The use of glass was strongly encouraged by Vice Admiral Robert FitzRoy, the melancholy man who commanded the Beagle with which Charles Darwin sailed around the world. In 1854 FitzRoy was placed in charge of the newly established Meteorological Office. He was convinced that there was a fixed relationship between the weather and the erratic appearance and disappearance of the – sometimes beautiful – white camphor crystals in the glass. He attributed it to electrical influences. Michael Faraday himself had to explain to him that that was nonsense and that the camphor crystals simply responded, but with a delay, to changes in temperature.

It has also been ruled out that the storm glass, as has been and is claimed, would be sensitive to changes in air pressure, and would therefore be a kind of ‘barometer’. The test tube is hermetically sealed and consists of thick glass.

Completely worthless

Modern research in Germany and Australia has failed to demonstrate any relationship between the changes within the storm glass and those of the weather outside. As weather forecasters, the storm glasses are completely worthless. With some good will you could deduce the previous temperature from the thickness of the layer of sediment that accumulates at the bottom of the glass, but that is of course not of much use. Yet seafarers used storm glasses until the 1930s.

The storm glass is not useful, but interesting, that’s the way it is. The oldest prescription for the preparation of the camphor tincture in the glass is from 1791. It is German and uses poorly defined units such as Lot and Quent. Later and more understandable problems do not seem to differ much from this. The camphor is always dissolved in advance in pure alcohol because this is not possible in water. The two salts, which in turn dissolve poorly in alcohol, are first absorbed in water. Approximately equal amounts of the two solutions are then brought together.

If the right amounts are used in the right proportions, the tincture is clear at high temperatures and when cooled a cloudy appearance occurs from which visible crystals gradually grow. The two salts promote that process because they reduce the solubility of camphor in the alcohol-water mixture. That’s called ‘salting out’ (salting out) and it therefore seems that this tool from organic chemistry was already known to the alchemists. In 1770 the modern chemistry of Lavoisier, Priestley and Dalton had yet to take shape.

Nice similarities

Chemists presumably attribute the fact that identical storm glasses behave differently under identical conditions to the role of crystallization nuclei that are necessary for smooth crystallization of the camphor. If the work has been done too cleanly, there may be a shortage of crystallization nuclei.

The strange truth is that the behavior of camphor, nitrate and chloride in the alcohol solution is not yet well understood, but there is not much interest in it either. A Japanese group led by Kazushige Nagashima sometimes does some research. There are quite a few similarities between the behavior of the camphor in the storm glass and that of the anise-like anethole in highly alcoholic liqueurs such as Pernod, Ricard and Pastis 51. Anethole can also be released from the Pernod if it is cooled too far. Or if water is added, as is common. It has been described here before.

The leaflet of the beautiful storm glass in the photos (which comes from Kikkerland) advises the buyer to first heat his glass with a hairdryer after receipt so that the contents are completely clear. It can then quietly precipitate ‘white matter’. Kikkerland does not mention the word camphor.


Because the hairdryer had been lent, the storm glass was heated to fifty degrees in a water bath last week. Moving on seemed risky. The contents did not become crystal clear, but a thin mist of fine droplets formed that slowly floated to the top and combined at the surface into a separate liquid layer. Later the layer solidified and slowly sank downwards. The course of events, which is not mentioned in the literature, has confused the AW editors. What did that extra liquid layer consist of? Camphor only melts at 175 degrees. Isn’t there any camphor in Kikkerland’s camphor glass? Why aren’t the ingredients of the storm glass simply mentioned? This needs to be investigated to the bottom.