Dr.Herbert Samuel Elworthy just wanted cold soda water to have with his drinks. In the 1890s he was working with the British Army Medical Corps and posted in Bandra, then on the margins of Bombay. From there he could easily head out for the hunting that was his passion, but hauling along ice and the heavy bottles of liquid carbon dioxide needed to make soda water was a problem.
Dr.Elworthy thought solid carbon dioxide could be an alternative. It had first been observed by Adrien-Jean-Pierre Thilorier, a French inventor who in 1830 had won a prize for devising an efficient apparatus to compress air. This created liquid carbon dioxide relatively easily allowing Thilorier to experiment with it. In 1835 he described how it formed a snowy substance when expressed into a closed glass jar.
Thilorier assumed this was frozen water, but another scientist correctly noted it was solid carbon dioxide. This had remained mostly a laboratory curiosity until Dr.Elworthy figured he could use it to both cool and carbonate water. He devised a process for manufacturing it safely and then transporting it to his camps. In 1897 he applied for a US patent where he noted how a lump dropped in water quickly carbonated it: “In this way the aerating machine with all its complications is completely done away with.” To cool liquids without carbonating them, the lumps just needed to be put in a metal box.
The patent application ensured that Dr.Elworthy’s pioneering role has been remembered – it is referred to, for example, in a long article on dry ice published in the 1930s entitled ‘109 Degrees Below Zero’ (its temperature in Fahrenheit). But nothing much happened until 1923 (by which time the patent had expired) when Thomas Benton Slate, an American inventor, started Prest Air Devices to sell compressed carbon dioxide for different uses, like extinguishing fires.
The breakthrough happened when Prest Air realised solid carbon dioxide could be an efficient form of cooling, particularly in transit, where liquid left by melting ice was a problem. Solid carbon dioxide turned straight into vapour, which lead to Slate’s second breakthrough – calling it ‘dry ice’, a term that was so successful that first the company was renamed after it, and then it became generic. (DryIce Corp. was unhappy about this but, unlike Dr.Elworthy, it never managed to get a patent for the manufacturing process so there was little it could do).
Dry ice quickly found uses. In 1926, for example, the Times of India (ToI) wrote about how Canadian fisheries were experimenting with it to flash freeze fish directly after it was caught. This prevents ice crystals growing that would damage the flesh and preserves it almost as good as fresh – this has allowed the spread of sushi restaurants around the world, using high quality flash frozen raw fish. Dry ice was used by vendors with ice cream carts, and could even be used, once packaged, to send frozen foods through post.
A dramatic use of dry ice is to add hot water to create thick vapours as special effects on stage, in nightclubs and live events. It became the standard way to depict icy mists in films, though sometimes this use backfired. In 1931 when Frank Capra directed Dirigible, a film about a race to reach the South Pole by air. Capra wanted to show the actors breaths freezing in the polar cold, but he was actually shooting it in September in New Jersey. He had little wire cages created with lumps of dry ice inside which the actors had to place in their mouths. This worked – until one of the lead actors swallowed a lump, leading to severe internal injuries.
Dry ice has been suggested as a humane pesticide to put in rat holes where the carbon dioxide it creates will knock out and suffocate rats. Dry ice blasting is a form of cleaning that is particularly effective for not leaving any residue. It has been tried for cloud seeding, the perennially hopeful attempt to create rain from clouds floating over dry regions. In 1983 Maharashtra’s government asked India’s main dry ice manufacturer to help seed clouds over reservoirs, because, unlike other chemicals, dry ice would leave no residue.
Dry ice has medical uses like freezing off warts and in cryogenics, like the freezing of the cord blood cells of newborn infants, for possible medical use later in their lives. But above all, it is used in medical cold chains, which will now become vital in the fight against Covid. All the vaccines being developed will need to be stored in cold containers until they are administered, but the variants using messenger RNA, like the one being developed by Pfizer, will have to be stored in superchilled containers, below -70 degrees Celsius, even when it goes into rural areas, and in less developed countries where even electricity is in short supply.
This will only be possible through extensive use of dry ice, and also liquid nitrogen. Parthasarathi Biswas wrote recently about how the use of bull semen transported in liquid nitrogen containers to dairy farmers across India is a model for how the vaccine roll-out can happen. Covid vaccination will have to replicate this at an immense scale, and dry ice will become essential. US producers are already warning about scarce supplies, partly because generally decreased manufacturing activity of products like ethanol which result in exhaust gases that are rich in carbon dioxide, which then become inputs for making dry ice. Dry ice might become an essential commodity.
This would have gratified Dr.Elworthy. He never saw much personal benefit from his patent, but in 1927 when the use of dry ice was picking up abroad ToI ran a story about how it had all been anticipated in India. For some reason he was not mentioned by name, but he was evidently “the citizen of Bombay, who was keen on shikar” who devised how to make dry ice and have it “sent to him daily, by post and runner, to his shooting camp in the CP” (Central Provinces, now Madhya Pradesh).
ToI noted that “the citizen” was still living in Bombay “and may in the near future see his thirty-year old dream come true. He was recently gratified to see in the American Chemical Society’s Journal an acknowledgment of the early attempts in India to introduce the use of the commodity.” And ToI concluded, in words that are even more true at a time when dry ice may help control Covid that “it is but right that India – and particularly Bombay – should receive credit where it is due.”
DISCLAIMER : Views expressed above are the author’s own.