Interesting fact, in England in 1851, the House of Lords was debating the proposed Sale of Arsenic Act, which required that purchasers of arsenic identify themselves and the amount of and purpose for the poison be registered in the vendor's records along with the purchaser's name. This act was prompted by Sarah Chesham who was responsible for many people all around her in her village dying. At this time arsenic was tinted with a warning color and purchasing required a written explanation and endorsement of a witness as well as purchasing a limited quantity.
Due to the publicity surrounding the Chesham murders, the House of Lords proposed an amendment to the act adding a clause restricting the sale of arsenic to adult males only.
The House of Commons had collected extensive statistics on gender and murder from all judicial districts in the United Kingdom between 1840-1850.
If you want to read an informative book on murder by poison and also on female murders, that dispels many myths, Female Serial Killers: How and why women become monsters by Peter Vronsky, very informative!