Berthollet the discoverer of bleaching by means of chlorine, and the chlorides, was a native of Savoy, and born in 1749, but emigrated and settled in Paris, where he was shortly atterWards made physician to the Duke of Orleans. Here he became the friend and competitor of the Lavoisiers, Fourcroys, Guiton de Morveaux, and Chaptals, and contributed, together with these latter, by his labors and discoveries, to bring about the brilliant change that was effected in chemistry and the arts. In 1794 he was named Professor of Chemistry at the Normal and Polytechnic Schools, and soon after the founding ot the French Institute he was selected as one of the number of talented individuals that first composed that learned body. He afterwards torm-ed part of the Scientific Commission that accompanied Napoleon Bonaparte in the expedition to Egypt, and on the accession of the Utter to the imperial power was made a Count and elevated to the dignity of Senator. These distinctions, which were conferred on him by the French Emperor were not given solely through fdvor, but as a recompense for his important services in the cause of industry, and for a multitude oi brilliant scientific discoveries, among which the law, so simple and prcisa, by which he determined the action of the salts on one another, would alone be sufficient to immortalize him. The process of bleaching vegetable matters by means of the chlorine and chlorides, for which we are also indebted to him, renders incalculable benefit to manufacturers from the rapidity which it allows of, in bleaching flix, hemp, and cotton yarns and. fabrics. Formerly it was necessary, inorder to bleach manufactured articles,to employ a method still adopted in some parts of France, which are still behind in industrial progress, and which consists in submitting the articles to the action of the lyes of potash or soda, and in exposing them afterwards for a suitable length of time to the moisture of the atmosphere by exposure in a field. By this exposure to the moisture ot the atmosphere most substances that color vegetable matters are deprived of their hydrogen, and having been by this means brought back to the state of acids, they are rendered soluble in alkaline lyes. The greasy matters, which are also in fabrics, are brought back by the absorption of the atmospheric air to the condition of fat acids, which are changed into soap and easily dissolve. But besides the very long time that this mode of bleaching required the ligneous matter that composes the thread,-underwent a noticeable alteration on account of the prolonged action of the humidity, and there was often developed on the surface of] linen cloths cryptogamic vegetation, the traces] of which it was afterwards impossible to get rid ot. Berthollet substituted for this system that which consists in dipping the yarn or fabric required to be bleached in a solution of liquid chlorine after having, however, been placed as mentioned above in alkaline lyes. The chlorine, when present with vegetable matters, decomposes the water in which it is dissolved, so as to form chlorohydric acid, and the oxygen proceeding from this decomposition serves to oxydize the coloring and oily matters, and thus render them soluble. This process, which, as may be seen, causes, like the old method, the bleaching ol linen by the oxydation of the coloring matters, offers the advantages of facility of execution in all seasons and with the greatest rapidity. The use of liquid chlorine presented, however, some inconveniences, by its easy evaporation it diminished the strength of the solution, and exercised a very hurtful influence over the workmen, that employed it. It is true that when the solution was weak most of these inconveniences did not show themselves, but then the little decolorizing power of these solutions was a great obstacle to the rapidity of the work. This is the reason that the hypochlorite of lime, commonly known as the chloride of lime, is now preferably employed. This salt, which is obtained by the action of chlorine in a gaseous form on lime, is in fact only a compound ot the hypochlorite of lime and chloride of calcium, a compound that often contains hydrate of lime, which, hav ing no chlorine, is entirely useless as a salt. The manner in which the hypochlorite of lime is employed is very simple, it is dissolved in water, and by means of an acid the chlorine is released, which, forming, as has been already said, hydrochloric acid, at the expense of the hydrogen in the water, sets at liberty the oxygen that deprives of color the vegetable matter. Carbonic acid should never be employed for this operation, but, on the contrary, a more energetic acid ; for the carbonic acid not decomposing the hypochlo rousacid, there would be obtained, for a result, only the carbonate of lime, chloride of eal-cium, and hypochlorous acid, without the disengagement of chlorine. Whilst if there is employed, for example, sulphuric acid, the hypochlorous acid is decomposed, the wholeof the lime, at the same time passing to the condition of a sulphate, and setting free the whole of the chlorine. The chloride of lime is easily changed by contact with the air and exposed to the action of light and moisture, it is therefore usual to buy it only according to its composition, that ia to say; according to the quantity of chlorine that it contains. For this purpose recourse mast be had to the chloro-metric experiments that Gay Lussac first pointed out, and by means ot which the quantity of chlorine contained in a given weight of hypochlorite of lime can be determined with exactness and precision. These experiments, which, the shortness of the article does not allow of our describing in this place, are based on the property that chlorine possesses, of changingj hy its passage to the condition of chlorohydric acid, arsenious acid, into arstnic acid. Experience has shown that cotton fabrics lose, on a mean, in the process ot bleaching, 28 per cent, of their weight, the loss that articles made of flax and hemp are subjected to, varies from 28 to 30 per cent. Berthollet first made known the composition of the hypochlorite of potassium better, known as the Eau de Javelle, and the employment of which, for bleaching purposes, is so extensive; this ingredient is easily obtained by immersing chlorine in a gaseous state in a solution of carbonate of potassium, for this purpose a very weak solution of potassium must be employed. In like manner the liquid employed by musical string makers, to prevent the putrefaction of the animal fibres, is only a hypochlorite of soda, which is obtained by mixing the chloride of lime with the carbonate of soda, it is, in fact, the Eau de Javelle made with soda, and is therefore cheaper. These various salts, from permitting the disengagement of gaseous chlorine, possess the property of purifying the air when spoiled by putrid substances. It \as beneficially employed, in 1815, by M. Thetard, to arrest the progress of an epidemic thaiwas committing great ravages in a portionof Holland. Fourcroy had previously reconmended the employment of chlorine for puifying dissecting rooms and stables in cases f epizooty. The woik entitled Statistical Chemistry, in which Berthollet recountedmost of his discoveries, is and will remain oneDf the most important works that have been 3ublished in chemistry. He retired from aoive life in 1807, to Arcueil, where he foundid a society composed of physicians and cheirists, who had been his pupils, and who publisled. under the title of Memoirs of Physici and Chemistry of the Society of Arcueil, ? scientific collection, in which are described the greater part of the discoveries of that period. Berthollet, made Peer of France in 1814, died Nov. 6,1822, at 63 years of age. He was a man of talent and genius, and the probity and disinterestedness which healwayi exhibited, acquired for him universal admiration and esteem. This pro-, cess for bleachinj by chlorine might have enriched him, but lie preferred making it public —all the advantage that he derived consisting in a few articles bleached by his process, which an English manufacturer sent to him as a present.—Invention.
This article was originally published with the title "Biography of Berthollet" in Scientific American 8, 26, 202 (March 1853)