(Bertrand), was born at Bayonne Mathematician in 1761, and very soon began to display an infatiable thirst of science. It frequently happens, however, that young men, sincerely desirous of instruction, have no means or place where they can be assisted in the development of their natural talents; no matter who may point out the direct road to science, and that order and method, without which the efforts of the individual too often lead him from the object of his pursuit, instead of bringing him nearer to it. This was not the case with young Pelletier. He found every advantage in his father's house, where he received the first elements of the art of which he was afterwards the ornament; and his subsequent progress was made under Darect, who having remarked in him that eagerness which may be called the instinct of science, admitted him among the pupils attached to the chemical laboratory of the college of France. Five years of constant application and study under such a master, who was himself formed by nature, perfected by experience, and affectionately disposed towards his pupil, afforded this young man a stock of knowledge very unusual at his age. He soon gave a convincing proof of this, by publishing, at the age of 21, a set of very excellent observations on the arsenical acid. Macquer, by mixing nitre with the oxyd of arsenic, had discovered in the residue of this operation a salt soluble in water, susceptible of crystallization in tetrahedral prisms, which he denominated the neutral arsénical It is the arsenic of potash. He was of opinion that no acid could decompose it; but Pelletier showed, that the sulphuric acid distilled from it does disengage the acid of arsenic. He showed the true cause why the neutral arsenical salt is not decomposable in closed vessels; and particularly the order of affinity by which the salt itself is formed in the distillation of the nitrate of potash, and the white oxyd of arsenic. He explains in what respects this salt differs from what Macquer called the liver of arsenic. Pelletier had been anticipated in this work by Scheele, by Bergman, by the academicians of Dijon, and by Berthollet; but he possessed at least the merit, in the first essay of his powers, of having clearly developed all the phenomena of this operation, by retaining and even determining the quantity of gas it was capable of affording. After the same principles it was that he decomposed the arsenico-ammonical salt, by showing how, in the decomposition of this salt, the pure arsenical acid is obtained in the form of a deliquescent glass. In this work we may observe the sagacity with which he was enabled to develop all the phenomena of these compositions and decompositions, by tracing those delicate threads of scientific relation which connect the series of facts, and are imperceptible to ordinary minds.

Encouraged by the success of these first works, which he presented with the sensibility of grateful attachment to his instructor, he communicated his observations on the crystallization of sulphur, cinnabar, and the deliquescent salts; the examination of zeolites, particularly the false zeolite of Fribourg in Brifgaw, which he found to be merely an ore of zinc; observations on the dephlogisticated or oxygenated muriatic acid, relative to the absorption of oxygen; on the formation of ethers, particularly the muriatic and the acetous; and several memoirs on the operation of phosphorus made in the large way; its conversion into phosphoric acid, and its combination with sulphur and most metallic substances.

It was by his operations on that most astonishing production of chemistry, phosphorus, that he burned himself so dangerously as nearly to have lost his life. After the cure of his wound, which confined him to his bed for six months, he immediately began the analysis of the various plumbagons of France, England, Germany, Spain, and America, and found means to give novelty and interest to his work, even after the publication of Scheele on the same object. The analysis of the carbonat of barytes led him to make experiments on animals; which prove that this earth is a true poison, whether it be administered in the form of the native carbonat of barytes, or whether it be taken from the decomposition of the sulphat, even though again combined with another acid.

Chemists have given the name of stonton to a newly discovered earth, from the name of the place where it was first found. Pelletier analyzed it, and discovered it in the sulphat of barytes. He likewise analyzed the verditer of England, of which painters and paper-hangers make so much use. He discovered a process for preparing it in the large way, by treating with lime the precipitate obtained from the decomposition of nitrat of copper by lime. By his process, verditer is afforded equal in beauty to that which comes from England. He was likewise one of the first chemists who showed the possibility of refining bell metal, and separating the tin. His first experiments were made at Paris; after which he repaired to the foundry at Romilly, to verify them in the large way. The following year he was received a member of the Academy of Sciences at Paris, and shortly afterwards went to La Fere, with Borda and General Dabouville, to assist in experiments upon a new gunpowder. Being obliged, in order to render his experiments more decisive, to pass great part of the day in the open air during a cold and humid season, his health, which was naturally delicate, became considerably impaired. He began to recover his health, when he again became the victim of his zeal for the science he so successfully cultivated. He had nearly perished by respiring the oxygenated muriatic acid gas. A violent attack of convulsive asthma, which returned during several days, was the first consequence of this unhappy accident. The disorder then seemed to abate; but it was incurable. The assistance of art was insufficient to save him; and he died in Paris, on the 21st of July 1797, of a pulmonary consumption, in the flower of his age.