Detective Narasimhan stepped into the strange red light that bathed the room. The wall facing him was lined with wide chemical-stained basins and strings hung overhead across the length of the room. The victim had been developing photographs in his last moments, Narasimhan surmised.
The body lay collapsed right in the centre.
He bent down to examine the victim and found that he was breathing in rapid, shallow spurts. He was unconscious, but alive. Narasimhan called quickly for the paramedics, who promptly carried him off just as he began to convulse.
By the wall closest to him was a stone shelf littered with bottles of chemicals. He read the labels: Potassium ferricyanide (K3[Fe(CN)6]), toner, thiourea (SC(NH₂)₂), and some other complicated names that are better left alone. Some of the bottles had been set aside, as if recently in use, and he knew these chemicals to be the ones used for sepia toning of photographs.
Rummaging through these for evidence, he accidentally tipped over the bottle labelled ‘water’. Something suddenly caught his eye. The liquid was beginning to corrode the shelf surface, and he couldn’t remember the last time he had heard about the ability of H2O to effervesce when poured on marble. This definitely wasn’t water.
He thought for a moment, and in a sudden wave of realization, he knew what had happened. He immediately grabbed the bottles marked ‘Sodium Thiosulfate’ and ‘Sodium Nitrite’ off the shelf and ran towards the ambulance into which the victim was being hauled. He administered the antidote, and soon enough, the man was alive and well. After all, there was a reason they called him the best forensic analyst in town.
So here’s what happened: The man had been poisoned.
The process of sepia toning takes place in three stages. First, the print is soaked in a potassium ferricyanide bleach to re-convert the metallic silver to silver halide. The print is washed to remove excess potassium ferricyanide and then immersed into a bath of toner, which converts the silver halides to silver sulfide.
Someone wanted the man dead, and whoever it was knew a thing or two about chemistry. The chemical in the bottle of ‘water’ wasn’t H2O, but concentrated hydrochloric acid (HCl). The perpetrator had replaced the water with acid, so that when added to potassium ferricyanide, it would liberate poisonous hydrogen cyanide gas (HCN), the same poison used in the gas chambers in concentration camps.
The reaction involved in the poisoning is as follows: 6 HCl + K3[Fe(CN)6] → 6 HCN + FeCl3 + 3 KCl Fortunately, the chemistry of the matter was discovered just in time to save a man from an untimely death. And better still, there was an antidote to cyanide poisoning:
Once again, Narasimhan had saved the day.
Chemistry is the science that explores how matter interacts with matter; and what results from these interactions.
A chemist’s strongest skill is that of observation; the ability to deduce the nature of matter through keen powers of perception and also, now, with specialised apparatus. Over the years, this heightened understanding of the substances that surround and constitute us has led to magnificent breakthroughs— like in metallurgy and medicine, for instance— that have revolutionised human existence.
Matter interactions are simply puzzles that chemists delight in solving using maths and physics as tools; and it only takes a little observation for the marvel of chemistry to reveal itself.
So join us as we unravel the mystery the matter.