Editing Mercury(II) chloride (section)

===Historical use in photography===
Mercury(II) chloride was used as a photographic intensifier to produce positive pictures in the [[collodion process]] of the 1800s. When applied to a negative, the mercury(II) chloride whitens and thickens the image, thereby increasing the opacity of the shadows and creating the illusion of a positive image.<ref>Towler, J. (1864). [http://albumen.conservation-us.org/library/monographs/sunbeam/chap18.html Stereographic negatives and landscape photography]. Chapter 28. In: [http://albumen.conservation-us.org/library/monographs/sunbeam/index.html The silver sunbeam: a practical and theoretical textbook of sun drawing and photographic printing. ] Retrieved on April 13, 2005.</ref>