William Crookes nació en Londres, Inglaterra, el 17 de junio de 1832. Fue el mayor químico de Inglaterra, según «Sir» Arthur Conan Doyle.Este ilustre hombre de ciencia desarrolló en el campo científico. Mencionado como uno de los más persistentes y valientes investigadores de los fenómenos supranormales, desarrolló importantes trabajos en el área de la fenomenología espírita.  En 1855, Willian Crookes ocupó la cátedra de química en la Universidad de Chester. Como resultado de prolongados estudios, en 1861 descubrió los rayos catódicos y aisló el talio, determinando rigurosamente sus propiedades físicas. Tras persistentes estudios del espectro solar, en 1872 descubrió la aparente acción repulsiva de los rayos luminosos, lo que le llevó a construir el Radiómetro en 1874. Al año siguiente descubrió un nuevo tratamiento para el oro. Sin embargo, la coronación de su obra científica fue el descubrimiento del cuarto estado de la materia, el estado radiante, en 1879. Recibió varias medallas por sus importantes descubrimientos en el campo de la física y la química.  La Reina Victoria de Inglaterra le honró con el título más alto de ese país: «Caballero «.  Además de todas sus actividades, fue presidente de la Sociedad Química, la Sociedad Británica, la Sociedad para la Investigación Psíquica y el Instituto de Ingenieros Eléctricos.

Endowed with an enviable investigative fibre, he eventually investigated mediumistic phenomena, at first with the aim of proving the error of the so-called "mediums" and of all those who firmly believed in their mediumship. In 1869, the mediums J.J. Morse and Mrs Marshall served as instruments for Crookes to carry out his first investigations. The most remarkable mediumistic experiments by this illustrious scientist were carried out through the medium Florence Cook, when he obtained materialisations from the spirit by the name of Katie King, which shocked the scientific world at the time. The young Florence Cook was only 15 years old when she presented herself to Sir William Crookes to act as a medium in the scientific investigations he was conducting. She said: "I went to Mr Crookes' house without telling my parents or friends. I offered myself as a voluntary sacrifice on the altar of his disbelief. She asked for Mrs. Crookes' protection and submitted herself to all sorts of experiments to prove her mediumship, as a gentleman named Volckmann had accused her of fraud. On 22 April 1872, Katie King's spirit materialised for the first time. Her mother, some of the medium's siblings and her maid were present at the séance.

After several spiritist séances in which the spirit of Katie King manifested itself with incredible regularity, Miss Florence told William Crookes that she was determined to submit to all sorts of investigations. In her work "Spiritist Facts", she gives a full account of all the experiments carried out with the materialised spirit of Katie King, which leaves no doubt as to the extraordinary power of the spirit to give the desired form using physical matter. Many renowned scientists, even in the face of the most convincing facts, hesitated to proclaim the truth, fearing the consequences it might have in the eyes of the people. Crookes, however, did not do this. He entered the field of research with the intention of unmasking, of finding frauds, but when he realised that the cases were true, he surrendered to the evidence, bowed to the truth, became a convinced spiritist, and asserted: - "I do not say this is possible; I say: this is real!"

 William Crookes died on 4 April 1919 in London, England.