Due to the big problems with accessing to the scientific literature published in the first half of the 19th century and even earlier, a deep invasion into the history of the subject still remains to be both fragmental and incomplete. That time, the scientific concepts were rather different from the modern ones and chemical formulae of the substances had not been introduced yet. Furthermore, scientific journals were rare; luckily, many scientific books published before the 20th century have been scanned by Google as a part of its project to make the world’s books discoverable online. This timely project by Google combined with the power of the modern electronic databases of scientific publications allows reconstructing the major historical milestones on calcium orthophosphates, which was often impossible for earlier writers. For example, a paper of 1994 by Driskell entitled: “Early history of calcium phosphate materials and coatings” [7] starts from the classical publication of 1920 by Albee assisted by Morrison [8]. In 1999, Shackelford published a paper: “Bioceramics — an historical perspective” [9], in which the same publication by Albee and Morrison [8] was mentioned as the earliest reference. The same is valid for the historical papers by Hulbert, et al. [10, 11] and Shepperd [12]. Thus, it seemed that calcium phosphates had been unknown before 1920. Certainly, this is not the case; nevertheless, the precise sequence of the scientific events happened in the 18thcentury still remain poorly restorable, while the historical time scale

of even earlier scientific events remain almost irrecoverable. This is mainly due to a lack of the citation practice existed in the scientific literature published in the 19th century and before. To the best of my findings, according to Shepperd [12], as early as in the end of the 18th century, a German chemist Martin Heinrich Klaproth (1743-1817) and a French chemist Joseph-Louis Proust (1754-1826) proposed that calcium phosphates were the major inorganic component of bones. Unfortunately, Shepperd has not provided any references to the publications by those great chemists. However, according to Roscoe and Schorlemmer [13], other researches had discovered this fact a bit earlier: “Gahn [14], in 1769, discovered the existence of calcium phosphate in bones, but it was not until this fact was published by Scheele [15] in 1771 that phosphorus was obtained from bone-ash, which has from that time invariably served for its preparation.” (p. 458). Furthermore, let me cite a publication of 1777 [16] (please, note the old-fashioned using a long, medial or descending letter “ſ”, which is a form of the minuscule letter “s” formerly used where “s” occurred in the middle or at the beginning of a word): “I have only been informed of this diſcovery, by the Gazette, Salutaire de Bouillon, October, 1775. It is there ſaid, that Mr. Henry Gahn, a phyſician at Stockholm, has communicated a proceſs for extracting from bones the ſaline matter in question; and that Mr. Scheele had aſcertained, that the earth of animals was compoſed of a calcareous ſubſtance united with the phoſphoric acid. This diſcovery, continues the author of the article of the Gazette, belongs to Mr. Gahn, and has been confirmed by later experiments." (p. 383). Presumably, this citation might be considered as one of the earliest mentioning on calcium phosphates. Furthermore, as written in a book by Lavoisier [17], the production process of orthophosphoric acid by decomposition of calcined bones in sulfuric acid has been known since, at least, 1790 (again, the old-fashioned replacement of letter “s” by "ſ”): “The bones of adult animals being calcined to whiteneſs, are pounded, and paſſed through a fine ſilk ſiewe; pour upon the fine powder a quantity of dilute ſulphuric acid, leſs than is ſufficient for diſſolving the whole. This acid unites with the calcareous earth of the bones into a ſulphat of lime, and the phoſphoric acid remains free in the liquor.” (p. 205). Further, the production process of white phosphorus has been described: “The liquid is decanted off, and the reſiduum waſhed with boiling water; this water which has been uſed to waſh

out the adhering acid is joined with what was before decanted off, and the whole is gradually evaporated; the diſſolved ſulphat of lime criſtallizes in form of ſilky threads, which are removed, and by continuing the evaporation we procure the phoſphoric acid under the appearance of a white pellucid glaſs. When this is powdered, and mixed with one third its weight of charcoal, we procure very pure phoſphorus by ſublimation.” (p. 206).