801 



CHEMISTRY. 



CHEMISTRY. 



803 



this period the white vitriol, or sulphate of zinc, was made, though its 

 composition was imperfectly elucidated. 



That sulphur was known before the age we are now treating of has 

 been already mentioned ; but in this period Basil Valentine describes 

 a solution of it in the fixed alkali, potash. Beguinus mentions it as 

 dissolved in the volatile alkali, or ammonia, and Vigenerus suspected 

 that it was composed of phlogiston and vitriolic acid. Basil Valentine 

 mentions the sulphuric and nitric ethers, but very slightly ; but 

 Crollius has described distinctly the art of preparing the former. 

 Thaddeus, Villanovanus, and Raymond Lully describe spirit of wine, 

 and the last calls the strongest spirit alcohol, a name which it yet 

 retains ; he mentions the separation of the water by means of carbo- 

 nate of potash, while Basil Valentine prefers lime for the same purpose. 

 Raymond Lully described the aerated volatile alkali, or carbonate of 

 ammonia. Aeriform bodies began to excite attention at this period. 

 Van Helmont noticed some of the properties of what he calls gas 

 sylvestre, or carbonic acid gas ; he observes that it is invisible, but 

 that it was fixed in bodies, and he attributes the phenomena of the 

 Grotto del Cane to its presence. 



From the middle till towards the end of the 17th century several 

 learned societies were formed. The Academy del Cimento was 

 founded at Florence in 1651, the Royal Society at London in 1660, and 

 the Academy of Sciences at Paris in 1666 : these societies greatly 

 promoted and advanced physics and experimental chemistry. In 1700 

 the Prussian Academy also took its rise, on the model of that of France. 

 Before, however, these societies existed, a curious work was published 

 in 1630 by Jean Rey, a physician of Perigord ; it is entitled ' Sur la 

 Recherche de la cause par laquelle Estaiu et le Plomb augmentent de 

 poids quand on les calcine." In this work, which excited little or no 

 attention among his contemporaries, the author, without apparently 

 making any experiments, but relying upon those of others, shows that 

 the weight which metals acquire during calcination is derived from the 

 i m in of air with the metal ; he supposes that air is miscible with other 

 bodies besides metals, and states that it may be expelled from water. 

 Rey is generally considered as the person who first showed that air is 

 fixed in bodies during calcination ; but in support of this opinion he 

 quotes Libavius, Cardan, and others, as having ascertained the increase 

 of weight in lead by its conversion into a calx. 



Newton himself contributed some new and general ideas on chemical 

 phenomena to the Royal Society ; he observes that sugar dissolves in 

 water, alkalies unite with acids, metals dissolve in acids, and he 

 inquires whether these effects are not occasioned by an attraction 

 between their particles. Copper dissolved in aquafortis is thrown 

 down by iron. Is not this, he inquires, because the particles of the 

 iron have a stronger attraction for the particles of the acid than those 

 of copper ; and do not different bodies attract each other with different 

 degrees of force ? 



The principal and early chemical investigators of the Royal Society 

 were Boyle, Hooke, and Slare. The first of these was the greatest 

 chemist and one of the most active experimenters of his age ; to him 

 the science is indebted for the introduction of tests, or re-agents, for 

 detecting the presence of other bodies ; he overturned the idea which 

 was then commonly entertained, that the results of the operation of 

 fire were the real elements of things. Respecting inflammable bodies, 

 acids, alkalies, and combination, he ascertained several important facts. 

 The air pump, which had been invented by Otto von Guericke of 

 Magdeburg, was improved by Boyle and Hooke, and rendered an 

 important instrument in chemical investigations respecting air ; they 

 concluded, also, that air was absolutely necessary to respiration and 

 combustion, and that a portion only of the atmosphere was employed 

 in these processes. Hooke, indeed, arrived at the sagacious conclusion, 

 that the part of the air necessary to the above-named processes is the 

 game as that contained in nitre, and that during the chemical process 

 of combustion this matter combines with the burning body. 



In 1674, Mayow of Oxford published his tracts on various philoso- 

 phical subjects. He seems to have been struck with the analogy 

 subsisting between the phenomena of respiration and combustion : 

 many of his conclusions were correct, though some of them were 

 erroneous. He burned a candle under a bell glass, and found the 

 residual air so deteriorated as to be incapable of continuing com- 

 bustion ; he then caused a mouse to breathe a similar quantity of air, 

 and the necessity of its renewal was soon apparent ; after this, he put a 

 mouse and a candle together under the same glass vessel, and he found 

 thai it lived only half as long as it had existed when alone under the 

 glass. He then reversed the order of experimenting, and endeavoured 

 to fire combustible matter in air which had been spoiled by breathing, 

 and finding no combustion took place, he concluded that " the nitro- 

 acrial particles are absorbed both by the candle and the animal." 

 Mayow's work contains a chapter relating to the " mutual action of 

 salts of a contrary kind," or to chemical combination and decomposi- 

 tion, A great number of new and curious facts are described in this 

 dissertation. 



Although a certain degree of similarity is observable in the views of 

 Boyle, Hooke, and Mayow, respecting the operations of combustion 

 and respiration, yet hitherto no theory had been attempted on a broad 

 basis to account for chemical phenomena. But about this period 

 Germany, which still continued the great school of practical chemistry, 

 gained additional credit by the labours of Beccher, who was born at 



ARTS AND 8CL DIV. VOL. It. 



Spires in 1645; he studied metallurgy and mineralogy with great 

 assiduity ; and although he did not greatly add to the collection of 

 chemical experiments, he improved the instruments of research, and 

 rendered manipulation more simple. His opinions were, that the 

 elements of bodies are air, water, and three earths, one of which is 

 inflammable, another mercurial, and another fusible; these three 

 earths, combined with water, he supposed to constitute a universal 

 acid which is the basis of all other acids. He entertained several other 

 notions which are now known to be utterly at variance with the results 

 of experiment ; his greatest merit was the contrivance of a theory by 

 which all known facts were connected and deduced from one .general 

 principle. This theory was adopted and considerably modified by 

 Stahl, and was by him promulgated in so imposing a form as to be 

 received by the chemical world almost universally for nearly a century. 

 We shall therefore now give a brief account both of this author and 

 his opinions, long known as the Stahlian theory. 



George Ernest Stahl was born in the year 1660, at Anspach. The 

 most important of his works is his ' Fundamenta Chymia: Dogmatics; 

 et Experimentalis,' which is divided into a theoretical and practical 

 part. The idea that the metals were earthy substances impregnated 

 with an inflammable principle had been advanced by Albertus Magnus. 

 Beecher maintained the existence of this principle, not only as the 

 cause of metallisation, but likewise of combustibility ; and Stahl much 

 improved this view of the subject, aud supported it by many iugenious 

 and elaborate experiments. To the peculiar principle he gave the 

 uaine of phlogiston ; the doctrine was called the Stahlian theory. It 

 raised the reputation of the author to the highest degree, and placed 

 him in the first rank of chemical philosophers. 



In explaining the phlogistic or Stahlian theory, it is to be under- 

 stood that Beccher and Stahl considered all combustible bodies as 

 compounds ; during combustion one of the principles is supposed to be 

 dissipated, while the other remains. Thus when charcoal is burnt, it 

 is entirely dissipated; Stahl therefore supposed that it was phlogiston, 

 or the inflammable principle, nearly pure. By heating charcoal with 

 metals which had been reduced to calces, or what were termed metallic 

 earths, they resumed their metallic appearance and properties ; there- 

 fore the metals are compounds of metallic earths and phlogiston. 

 Again, by heating Glauber's salt, which is a compound of sulphuric 

 acid and soda, or the fossil alkali, with charcoal, a compound of 

 sulphur and alkali was obtained. Sulphur, therefore, was supposed to 

 be a compound of sulphuric acid and phlogiston. Now, though it had 

 been shown by Boyle that sulphur would not burn without air, and 

 though he had stated that sulphur was contained in the acid, and not 

 the acid in the sulphur, yet Stahl entirely neglected, in forming his 

 theory, the influence of air in producing the phenomena on which it 

 was founded. The first promulgation of the theory overlooked the 

 simple fact which had been before stated, that metals, instead of 

 becoming lighter by being burnt, as ought to have happened had they 

 lost anything, actually become heavier by the operation. Those who 

 afterwards refined upon this theory endowed phlogiston with a 

 principle of levity, and thus the difficulty was for a time removed, 

 but only to be revived with redoubled force; and this difficulty, 

 when it came to be duly appreciated, proved fatal to the theory of 

 phlogiston. 



The merits of Stahl are thus briefly stated by Sir H. Davy : 

 " Though misled in his general notions, few men have done more than 

 Stahl, for the progress of chemical science. His processes were, many 

 of them, of the most beautiful and satisfactory kind ; he discovered a 

 number of properties of the caustic alkalies and metallic calces, and 

 the nature of sulphurous acid ; he reasons upon all the operations of 

 chemistry in which the gaseous bodies are not concerned, with admi- 

 rable precision. He gave an axiomatic form to the science, banishing 

 from it vague details, circumlocutions, and enigmatic descriptions, in 

 which even Beccher had too much indulged ; he laboured in the spirit 

 of the Baconian school, multiplying instances and cautiously making 

 inductions, and appealing in all cases to experiments which, though 

 not of the most refined kind, were more perfect than any which pre- 

 ceded them." 



Several chemists of the phlogistic school followed, who contributed 

 to the advancement of chemical science. Caspar Neumann was born 

 at Zullichau, in Germany, in 1682. In 1724 he was appointed pro- 

 fessor of chemistry in the Royal College of Physic at Berlin. 

 Dr. Lewis, in the year 1759, published a translation of his works, 

 entitled, ' The Chemical Works of Caspar Neumann, M.D.," &c. It 

 would perhaps be difficult to mention any very important discovery 

 contained in this work ; but there are several facts which, as facts 

 are always valuable, must still give it a place in the library of a 

 chemist. 



John Henry Pott was born at Halberstadt, in the year 1692, aud 

 died in 1777. On the death of Neumann, in 1737, he succeeded to 

 the chair of practical chemistry. He was a chemist of great learning 

 and industry. The greater part of his works were collected and trans- 

 lated into French in 1759. In his dissertation on bismuth and zinc, he 

 has collected the statements of all former writers, and described their 

 properties with minute accuracy. 



In the year 1709, Andrew Sigismuud Margraaf was born at Berlin : 

 he died in 1782. He made some valuable experiments on phosphorus, 

 and on the method of extracting it from urine ; he first determined the 



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