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Some contemporary reflections on the arsenic act 1851

By Irish Pharmacist - 02nd May 2020

Writing for Irish Pharmacist, Dr Bernard Leddy PhD MPSI looks back to a time when those selling arsenic were not required to have any formal education, training or registration — or the ability to write — in order to sell enough arsenic to kill 45,000 people

Pharmacists these days work and practice in a highly-regulated environment where the sale and supply of medicines and drugs are strictly controlled. But it wasn’t always like that. Before there were registered pharmacists and pharmacies, regulation was quite rudimentary. Before 1851 and Irish independence, the United Kingdom consisted of the countries of England, Scotland, Ireland and Wales. There were three separate jurisdictions within the United Kingdom, England and Wales, Scotland and Ireland.

The application of laws and the legal systems were often  slightly different. The Arsenic Act 18511 was enacted unchanged throughout the entire United Kingdom. The Pharmaceutical Society of Great Britain, which encompassed England, Scotland and Wales, was founded in 1841. The Pharmaceutical Society of Ireland, which encompassed all 32 counties of Ireland, was founded in 1875. 

I am not sure why there was a 34-year discrepancy between the establishment of the British and Irish Pharmaceutical societies. The Great Irish Famine started in 1845 and its effects continued until 1855, based on workhouse records. Great Britain did not suffer such a massive social and economic disruption at the same time. 

The Arsenic Act 1851 was the first legislation to control and regulate the sale and supply of a poisonous chemical. There were clearly concerns about the use, abuse, misuse of arsenic and its various salts and compounds. The Act doesn’t state a requirement for the seller to have any formal education, training or registration — a concept which would be inconceivable in today’s world. Also, there is no mention of a requirement that arsenic must be sold from a fixed premises.


The requirements to be met before the sale of any arsenic were as follows [capitalisation retained]: “Every person who shall sell any Arsenic shall forthwith, and before the Delivery of such Arsenic to the purchaser, enter or cause to be entered in a fair and regular Manner, in a Book or Books to be kept by such Person for that purpose, in the form set forth in the Schedule to this act, or to like effect, a statement of such sale, with the quantity of arsenic so sold, and the purpose for which such arsenic is required or stated to be required, and the day of the month and year of the sale and the name, place of abode, and condition or occupation of the purchaser, into all which circumstances the person selling such Arsenic is hereby required and authorised to inquire of the purchaser before the delivery to such purchaser of the Arsenic sold, and such entries shall in every case be signed by the person making the same, and shall also be signed by the purchaser, unless such purchaser profess to be unable to write (in which case the person making the entries hereby required shall add to the particulars to be entered in relation to such sale the words “cannot write” and where a witness is hereby required to the sale, shall also be signed by such witness, together with his place of abode.”

There are many interesting insights into the minds of those who constructed the Act. Literacy rates in the UK in 1851 were quite variable, depending on the location and occupation of adult males and females.2 The most comprehensive statistics come from parish marriage registers, where both the bride and groom are required to sign their names. 

Such registers show that literacy (ability to write your own name) rates varied widely, from about 40 per cent to over 90 per cent, depending on the geographical location of the parish. The situation in Ireland was somewhat different to the rest of the UK. The Act requires the seller of arsenic to be literate but not the purchaser, as the seller is required to write in the register of sales.

“No Person shall sell Arsenic to any Person who is unknown to the Person selling such Arsenic, unless the Sale be made in the Presence of a Witness who is known to the Person selling the Arsenic, and to whom the Purchaser is known, and who signs his Name, together with his Place of Abode, to such Entries, before the Delivery of the Arsenic to the Purchaser, and no Person shall sell Arsenic to any Person other than a Person of full Age.”

Full age in 1851 was 21 years old.

‘Provision for colouring Arsenic’

“No Person shall sell any Arsenic unless the same be before the Sale thereof mixed with Soot or Indigo in the Proportion of One Ounce of Soot or Half an Ounce of Indigo at the least to One Pound of the Arsenic, and so in proportion for any greater or less Quantity: Provided always, that where such Arsenic is stated by the Purchaser to be required, not for Use in Agriculture, but for some other Purpose for which such Admixture would, according to the Representation of the Purchaser, render it unfit, such Arsenic may be sold without such Admixture in a Quantity of not less than Ten Pounds at any One Time.”

The seller was required to colour the Arsenic with either soot or indigo. As arsenic trioxide is a white powder which may be confused with sugar or flour, adding a colour would make it distinguishable and hopefully avoid any accidental poisoning. However, the arsenic, if required to be colourless, may be sold in quantities of not less than 10 pounds (4.54Kg). Given that the lethal dose of arsenic is said to be between 100mg and 300mg, 10 pounds could potentially kill up to 45,000 people. Indigo is a blue dye which was originally obtained from plant sources but is now a synthetic chemical. This might have been difficult and expensive for some suppliers of arsenic to source in the 1850s, so an alternative colourant of soot was permitted.

‘Penalty for offending against this Act’

“If any Person shall sell any Arsenic, save as authorised by this Act, or on any Sale of Arsenic shall deliver the same without having made and signed the Entries hereby required on such Sale, or without having obtained such Signature or Signatures to such Entries as required by this Act, or if any Person purchasing any Arsenic shall give false Information to the Person selling the same in relation to the Particulars which such last-mentioned Person is hereby authorised to inquire into of such Purchaser, or if any Person shall sign his Name as aforesaid as a Witness to a Sale of Arsenic to a Person unknown to the Person so signing as Witness, every Person so offending shall for every such Offence, upon a summary Conviction for the same before Two Justices of the Peace in England or Ireland, or before Two Justices of the Peace or the Sheriff in Scotland, be liable to a Penalty not exceeding Twenty Pounds.”

Twenty pounds in 1851 equates to £2,747 today by calculation. The average weekly wage for a farm labourer in 1851 was nine shillings and threepence halfpenny. So a fine of £20 was nearly 50 weeks’ wages for a farm labourer; quite a hefty fine. Interestingly, there are no custodial penalties for breaching the Arsenic Act. Presumably, there were still penalties for not paying the fine.

‘Act not to prevent Sale of Arsenic in Medicine under a medical prescription’ 

“Provided, That this Act shall not extend to the Sale of Arsenic when the same forms Part of the Ingredients of any Medicine required to be made up or compounded according to the Prescription of a legally qualified Medical Practitioner, or a Member of the Medical Profession, or to the Sale of Arsenic by Wholesale to Retail Dealers, upon Orders in Writing in the ordinary Course of Wholesale Dealing.”

This is an interesting part of the Act, as it refers to the supply of Arsenic on a medical prescription or by way of wholesale dealing. There were pharmacies as we know them in Great Britain, as the Pharmacy Act, which established them, predates the Arsenic Act. The situation in Ireland is less clear, as the act which established Irish pharmacies wasn’t enacted until 1875.3 It appears that prescription compounding was done by an eclectic mixture of Apothecaries and Medical Halls and The Poor Law Dispensaries until 1875.

‘‘Arsenic’ to include arsenious compounds’ 

“In the Construction of this Act the Word “Arsenic” shall include Arsenious Acid and the Arsenites, Arsenic Acid and the Arsenates, and all other colourless poisonous Preparations of Arsenic.”

The legal definition of Arsenic as covered by the Act. It is noticeable that the Act only applies to colourless salts of Arsenic, so copper arsenate is not covered by the Act, as it is blue-green in colour and may be sold without restriction.

Summary of the arsenic act 1851

The motivation for bringing in the Arsenic Act 1851 was to limit and regulate the sale of colourless Arsenic compounds. The full title of the Act is ‘Sale of Arsenic Regulation Act 1851’, so the main motivation of the Act was to formally control and regulate the sale of arsenic. There are many cases recorded where arsenic was suspected in being involved in poisonings, but it wasn’t until the Marsh Test4 was developed in 1834 that an analytical method of detecting arsenic in pathology samples was developed. 

One of the most famous mass poisonings with arsenic occurred in 1858. The ‘Bradford sweets poisoning’5 was the arsenic poisoning  of more than 200 people in Bradford, England, when sweets accidentally made with arsenic were sold from a market stall. Twenty-one victims died as a result.

The event contributed to the passage of the Pharmacy Act 18686 in the United Kingdom and legislation regulating the adulteration of foodstuffs. 

The confusion arose when a messenger was sent to a pharmacy to buy gypsum, which the confectioner used to reduce the amount of expensive sugar used in making the sweets. A junior assistant in the pharmacy mistakenly sold him arsenic trioxide instead. Arsenic trioxide was an odourless and virtually tasteless white powder which could be easily mixed with food or drink. As the seller did not require any training or qualification, it is not surprising that mistakes were made. This changed with the 1868 pharmacy act.

This was the first enactment in the United Kingdom which sought to regulate and control the sale of a specific poison.

References on request.






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