THE FOLLOWING ARTICLE APPEARED IN THE

JULY 1999 ISSUE

THE POISON SLEUTHS

DEATH BY OXALIC ACID

-Dr. Anil Aggrawal

"Good morning doctor. Oh, my God, what are you doing today? You have the dead body of a middle age man today. He shows some strange marks around his mouth. How did he die? Please let me know."

"Good morning Tarun. The name of this unfortunate man is RadheyShyam. He is about 45 years old. He is living in a slum cluster of Delhi for the last several years. Some years back he was a fairly well-to-do man, but then suddenly his fortunes took a turn and he became quite poor. His wife and children deserted him, and he came to live in a shady slum cluster. He used to pick up odd jobs for his livelihood. He was very much in debt too, for the last so many months."

"Oh, so you think one of his creditors killed him?"

"I didn't say that. Although the police is investigating along those lines. He had taken about Rs. 25,000 from one Kale over a period of last few months, and Kale was pressing him to give his money back. Radhey Shyam had no means to pay him back his money. Yesterday night Kale had visited him. Everybody in the slum cluster saw him coming to his house and then leave surreptitiously. Nobody thought that he would go to such an extent as to kill him. Radhey's dead body was found in his house today morning. For all intents and purposes, it appears that it is Kale who has killed him."

"So he killed Radhey Shyam, when he realized he is not going to get his money back. Perhaps it was his way of telling his other debtors that they must pay up or face dire consequences?"

"Again this is the line police is investigating on. The police has arrested Kale and are questioning him. But Kale is swearing he did not do anything to Radhey Shyam. He does admit that he went to Radhey's house, but he simply gave a threat and came back. But police does not agree with his version. As for me, I generally don't give my opinion till I have examined all the facts, and especially till I have done the post-mortem. I have seen some strange things in this case, which tells me that it is probably not a case of homicide, but of suicide."

"What makes you think that?"

"Tarun, look at the strange whitish streaks running downwards from his mouth. You yourself remarked about them, when you first came here. Do you know what they are? They are in fact corrosion lines generally found when a person drinks acid. And let me tell you, acid is so corrosive, it is almost impossible to give it homicidally. Acid can only be taken by a person who wants to commit suicide. For instance if Kale had wanted to give Radhey this acid, he couldn't have done so, even if he had brought it mixed in some foodstuff, say, milk. The reason is that Radhey would have immediately discarded the milk after just the first sip."

"So you think Radhey drank this acid to kill himself. But why would he do that?"

"Radhey was upto his neck in debts. So it doesn't seem entirely confounding that he committed suicide. The question is which acid did he drink. And if we can find the half empty bottle of that acid from his house, our work is done. Finding a bottle of corrosive in the house is another proof that Radhey did commit suicide. Had Kale by any chance given him the acid, he would not have committed the blunder of leaving the bottle behind."

"Yeah that seems fairly plausible. Which acid did he drink doctor? I am sure that this is an important question for you to answer, because the police as well as the court would be very interested in knowing the answer to this question."

"Tarun, I have examined the stomach and kidneys of Radhey. And I have come to the conclusion that Radhey has drunk Oxalic Acid."

"What? Oxalic Acid? Doesn't sound like a very common suicidal poison to me. How in the world did he get hold of Oxalic acid in the first place?"

"Tarun, Oxalic acid is a constituent of many household products. It is found in many disinfectants, household bleach, metal cleaning liquids, antirust products and furniture polish. Its chemical formula is (COOH)2. Oxalic acid is a crystalline, colourless substance which is efflorescent. This means that it tends to become powdery on account of loss of water of crystallization. Its solubility is 1 in 12 in water. It is called Oxalic acid, after Greek "oxalis", which means sorrel. It occurs in the sorrel plant, and because of this the French chemist Lavoisier, in 1787, named it Oxalic acid."

"Oh, that is really very interesting. Does it occur in other plants too?"

"Oh yes. It occurs in the leaves and young stalk of rhubarb (Rheum rhaponticum), spinach and even cabbage. I must tell you that sorrel is a succulent acid herb used in salads. Accidental poisoning has been known to occur after a hearty meal of rhubarb or sorrel. Food rich in oxalate can also lead to kidney stones, because kidney stones are generally made up of oxalates."

"Oh, that is really very interesting information."

"Tarun, crystals of oxalic acid are similar in appearance to those of magnesium sulphate - also known as Epsom salt- and zinc sulphate. Because of this similarity, cases of accidental poisoning have occurred. Magnesium sulphate in doses of 15 g is used as a laxative, and is non-toxic. Since oxalic acid - a dangerous poison - is so similar looking to Epsom salt - a commonly used drug - it is necessary to be able to differentiate between the two. If the doctor or the nurse fails to differentiate between the two, accidental poisonings may occur. You may be interested to know that two patients at a mental hospital in Scotland died in 1956 after receiving doses of oxalic acid administered in mistake for Epsom salts. Zinc sulphate is also a commonly used drug. It has been used in such skin diseases and infections as acne, ivy poisoning, lupus erythematosus, and impetigo. Don't worry about the confusing disease names. What I want to impress upon you is that even zinc sulphate is a commonly used drug, and whenever a commonly used drug looks very similar to a dangerous poison, it becomes very necessary to be able to differentiate between the two."

"So how do doctors differentiate between the two?"

"Well, if you taste a small amount of crystal of each, oxalic acid is sour in taste, magnesium sulphate is nauseatingly bitter and zinc sulphate is metallic bitter. But surely, this is not the best of the methods to find out a poison. The reaction of oxalic acid is strongly acidic, that of zinc sulphate is slightly acidic, and that of magnesium sulphate is neutral. On application of heat oxalic acid sublimes while the rest of the two salts remain fixed. When you react each salt with sodium carbonate, oxalic acid shows effervescence, but no precipitation, while the other two salts show no effervescence, but a white precipitate. But perhaps the easiest test is to see if stains of ink or iron moulds disappear by a solution of one of these salts. While a solution of oxalic acid makes the stains disappear, the other two salts can not do that. In fact, that is why oxalic acid is used in products like ink removers and furniture polishes. Oxalic acid, as I have already told you, is used in households as a bleach to remove stains or to clean metals, notably brass or leather, and also in calico-printing. It was widely used when the straw hat industry flourished, during 1880-1910. Potassium oxalate is also used to remove ink stains and to cleanse metals. Solutions of oxalic acid and oxalates should never be left unguarded, since the colourless, and odourless fluid may readily be mistaken for water. However the taste is sour as I have already told you, so an unsuspecting person may take it, but would be quick in discarding it."

"Can oxalic acid be used for homicide?"

"No Tarun, that is not possible. That is why I think Kale is innocent. Because of its sour taste, it has not been used for homicide very much. Oxalates have however been used to procure abortion by vaginal injection. This is done by quacks who are approached by unmarried girls who have conceived due to premarital relations. But I may tell you that now no girl needs to contact such quacks. Now the law allows even unmarried girls to approach a properly qualified doctor in a government hospital to have an abortion done."

"Doctor, how does oxalic acid affect the human body?"

"Tarun, oxalic acid has both a local, and a systemic action on the body. By local action, I mean the action of stomach and intestinal walls with which it comes in contact. By systemic effect, I mean remote effect on organs with which it does not really come in contact. Oxalic acid readily corrodes the mucous membrane of the digestive tract. Unlike corrosive mineral acids and alkalies - like hydrochloric acid, sulphuric acid and nitric acid, oxalates do not lose their poisonous properties when diluted. On the contrary, dilute solutions of oxalates, can cause grave systemic effects. Oxalic acid however rarely damages the skin."

"So these are the local effects of oxalic acid. What are its systemic effects?"

"Large doses of oxalic acid can cause death due to shock. Oxalates can readily combine with the calcium ion in the body tissues, causing a precipitous fall in the level of ionized calcium. This can cause muscle irritability, tetany and convulsions, and irregular action and slowing of the heart. I may remind you that all muscle cells in the body are very much dependent on calcium for their proper functioning, and it includes heart muscle too."

"Yeah I do know about that. Doctor, what are the signs and symptoms of oxalic acid poisoning?"

"The symptoms of oxalic acid poisoning are modified by the size and concentration of the dose. A large concentrated dose would kill within a couple of hours by shock or hypocalcaemia, i.e. lowering of calcium levels in the blood. A large dilute dose would cause kidney failure. Depending on the size and concentration of dose, the clinical picture may vary. Fulminant poisoning occurs when a large concentrated dose of about 15 gms or more is taken. This is actually the lethal dose of oxalic acid. The clinical picture is dominated by gastrointestinal symptoms. There is immediate sour or bitter taste, associated with a burning sensation in the mouth, throat and food pipe because of the corrosive action of oxalic acid. Agonizing pain in the epigastrium, which soon spreads all over the abdomen associated with tenderness is seen. There is eructation, distension of abdomen, thirst, nausea and vomiting. The vomitus has a "coffee ground" appearance, because oxalic acid badly corrodes the stomach walls. There may be bloody vomiting for the same reason. Finally shock supervenes and death occurs. Acute poisoning occurs when a moderately large dose is taken and in such cases, the survival is upto 48 hours. The clinical picture is dominated by symptoms due to hypocalcaemia rather than due to gastrointestinal upset. These are muscle irritability, tenderness, tetany, convulsions, numbness and tingling of the finger tips and legs, cardiac irregularity, slowing of the heart, ventricular fibrillation (irregular and fast beating of the ventricles of the heart). In some patients, oxalates may have a narcotic effect. Delayed poisoning may occur when a smaller dose is taken. The clinical picture is characterized by symptoms of renal failure and uraemia. Death occurs in 5-14 days. I may tell you that the fatal dose of oxalic acid is about 15-20 gms, and the fatal period is 1-2 hours."

"Doctor, in the case of Radhey, how exactly did you make out that it was a case of oxalic acid poisoning?"

"Tarun, my first lead was given by these strange streaks running downwards from the angles of the mouth. Burns of the skin are actually quite rare in oxalic acid poisoning. Corrosion of the mucous membrane of the GIT, starting from lips is common. There is whitening or yellow-white discoloration of the lips, lining of the mouth, and upper surface of the tongue. The mucous membrane of the mouth gives an appearance similar to scalding. This is exactly the picture that I saw in Radhey Shyam. Then I got curious and did the post-mortem. I was very much interested in seeing his stomach. The lining of the stomach in oxalic acid poisoning is blackened by the production of acid haematin. There may be superficial corrosion. The stomach may contain fresh or altered blood. Furthermore, crystals of calcium oxalate can be demonstrated in scrapings of the stomach mucosa. Radhey Shyam's stomach showed all these findings, and I even could chemically demonstrate oxalic acid crystals sticking to his stomach mucosa. The kidneys of a person dying of oxalic acid poisoning are congested and swollen with oedema. The tubules contain oxalate crystals. The renal tubules are necrosed, which in plain and simple terms means that they are dead. I could demonstrate oxalic acid crystals even in the renal tubules of Radhey. I am sure it is a case of Oxalic acid poisoning. Lo and behold, here comes the policeman with the half empty bottle of Oxalic acid from Radhey Shyam's house. I had earlier sent him to Radhey Shyam's house to look for oxalic acid bottle. Now it is clear that it is a case of suicidal poisoning by oxalic acid. The police will now not harass Kale and would release him from custody."

"Oh yeah, I am sure, the police will do that. This was a most interesting discussion doctor. Tell me what are you going to tell me the next time?"

"Tarun, next time, I would tell you about a very interesting poison- Digitalis. "