full visibility by mercury fumes. This brought the required exposure time down to a few minutes under optimum conditions. A strong hot solution of common salt served to stabilize or fix the image by removing the remaining silver iodide. On 7 January 1839, this first complete practical photographic process was announced at a meeting of the French Academy of Sciences, and the news quickly spread. At first, all details of the process were withheld and specimens were shown only at Daguerre's studio, under his close supervision, to Academy members and other distinguished guests. Arrangements were made for the French government to buy the rights in exchange for pensions for Niépce's son and Daguerre and present the invention to the world (with the exception of Great Britain, where an agent for Daguerre patented it) as a free gift. Complete instructions were made public on 19 August 1839. Known as the daguerreotype process, it was the most common commercial process until the late 1850s when it was superseded by the collodion process. French-born Hércules Florence developed his own photographic technique in 1832 or 1833 in Brazil, with some help of pharmacist Joaquim Corrêa de Mello (1816–1877). Looking for another method to copy graphic designs he captured their images on paper treated with silver nitrate as contact prints or in a camera obscura device. He did not manage to properly fix his images and abandoned the project after hearing of the Daguerreotype process in 1839 and did not properly publish any of his findings. He reportedly referred to the technique as "photographie" (in French) as early as 1833, also helped by a suggestion of De Mello. Some extant photographic contact prints are believed to have been made in circa 1833 and kept in the collection of IMS.Henry Fox Talbot had already succeeded in creating stabilized photographic negatives on paper in 1835, but worked on perfecting his own process after reading early reports of Daguerre's invention. In early 1839, he acquired a key improvement, an effective fixer, from his friend John Herschel, a polymath scientist who had previously shown that hyposulfite of soda (commonly called "hypo" and now known formally as sodium thiosulfate) would dissolve silver salts. News of this solvent also benefited Daguerre, who soon adopted it as a more efficient alternative to his original hot salt water method. Talbot's early silver chloride "sensitive paper" experiments required camera exposures of an hour or