560 



BLACK. 



Black duct of Mr Lavoisier, ahd vindicating his undoubted 

 ~ v"-* claim to his own discoveries. He undertook the task, 

 and began it repeatedly ; but his anxiety never failed 

 to bring on a fit of illness, which obliged him \o re- 

 linquish it. What reason he had to be dissatisfied with 

 Lavoisier, or what private steps that celebrated phi- 

 losopher may have taken to detract from Dr Black's 

 reputation, we pretend not to say. Lavoisier certain- 

 ly did Dr Black ample justice in the first treatise on 

 chemistry which he published ; for the whoL- treatise 

 is little else than a history of Dr Black's discoveries 

 with respect to the alkalies and lime, of the contro- 

 versy which these discoveries occasioned in Germany, 

 and a recitation of his own experiments, which con- 

 vinced him of the truth of Dr Black's opinions. Of 

 Dr Black's discoveries in other branches of the 

 science, Lavoisier could not be supposed to know 

 much with accuracy ; for Dr Black hid published 

 nothing respecting them himself, and those writers 

 who had touched upon these subjects, whether in 

 Britain or on the continent, had been either silent 

 with respect to Dr Black's merit as an original dis- 

 coverer, or arrogated to themselves an equal claim to 

 originality with Dr Black himself. 



As to Dr Black's private character, it was, in the 

 highest degree, amiable and excellent. His temper 

 was mild and placid ; his disposition serious but 

 cheerful. His sense of propriety was extremely acute, 

 and all his actions were obviously guided by it. This 

 appeared to a striking degree in his dress, in his house, 

 at his table, in company, and in his lecture room. 

 Every thing was done at its proper time; every thing 

 was found in its proper place. He was never in a 

 hurry, but always appeared to have leisure at com- 

 mand ; and he was always happy to see a friend, and 

 to enter into conversation on general subjects. His 

 acquaintances sometimes accused him of penurious- 

 ness ; but Dr Ferguson, who was his near relation, 

 and had the best opportunity of knowing his charac- 

 te% directly denies the charge ; and Professor Robi- 

 son has given such instances of a contrary conduct, as 

 seem totally incompatible with such a disposition. 

 His person was rather above the middle size ; he was 

 of a slender make ; his countenance was placid, and 

 exceedingly engaging. 



But in giving the history of a literary character, 

 the points of greatest importance are undoubtedly his 

 works, which constitute the grand eras of his life. 

 In a philosopher, the additions which he made to the 

 stock of our knowledge, and the exertions which he 

 made towards the advancement or the general diffu- 

 sion of the sciences, constitute the great characters 

 which distinguish him from the generality of man- 

 kind. We must not, therefore, quit Dr Black, with- 

 out pointing out his literary labours more particular- 

 ly, and endeavouring to estimate the obligations 

 which chemistry lies under to him for his sagacity 

 and discoveries. 



If we were to estimate the merits of a literary man 



from the bulk of his writings, Dr Black would be 



r;'*ed very low. The only pieces which he published 



in his life-time were four essays: 1st, His inaugural 



' ion, entitled, De -acido a cibis orto et k mng- 



csia; i.'d, Experiments upon magnesia alba, quick- 



lime, and other alkalitt? substance:, frrit published in 

 the Edinburgh Physical and Literary Essays in 1755, 

 and afterwards in a separate form by Mr Creech ; 3d, 

 Observations on the more ready freezing of water that 

 has been boilr.d, published in the Philosophical Trans- 

 actions of London for 1774' j and, 4th, Analysis of 

 the waters of some boiling springs in Iceland, publish- 

 ed in the second volume of the Edinburgh 7'ransac- 

 tions. After his death, his manuscript L-cturcs were 

 revised by Professor Robison, and published by his 

 executors in two quarto volumes. This book poi- 

 sesses great merit, especially the first part of it which 

 treats of Heat. The simplicity of the style, and the 

 exquisite taste and propriety displayed in the illus- 

 trations, cannot be too highly praised ; though, as a 

 whole, it is certainly very different from what it would 

 have been, had it received the last corrections of the 

 author himself. The arrangement in many parts is 

 extremely defective ; and, as a collection of chemical 

 facts, it is nearly twenty years behind the period at 

 which it finally appeared. Had it been published in 

 1788, it would have contributed essentially to pro- 

 mote the progress of the science ; it would have in- 

 creased the reputation of its author, and been a high- 

 ly popular book even in the hands of the students ; 

 but, in 1803, its place was supplied by others, exhi- 

 biting a fuller detail of chemical facts, and bringing 

 the progress of the science down to the date of their 

 publication. 



In taking a view of these different publications, we 

 may pass over the first entirely. The second was, 

 in fact, a repetition, or rather a more complete inves- 

 tigation of the different points touched upon in the in- 

 augural dissertation. 



1. The essay on magnesia and quick-lime embraces 

 two distinct objects: 1st, The properties of magne- 

 sia ; 2d, An investigation of what constitutes the 

 difference between quick-lime and limestone, between 

 the mild and caustic alkalies. 



Magnesia had been discovered by a Roman canon, 

 at Rome, about the beginning of the last century, 

 and a few of its properties had been ascertained by 

 Frederick Hoffmann ; but chemists, in general, con- 

 sidered it as a. variety of lime, and none knew the pe- 

 culiar characters by which it is distinguished. Dr 

 Black ascertained its properties with precision, and de- 

 monstrated that it is a peculiar earth. To him, there- 

 fore, in reality, we are indebted for our knowledge of 

 magnesia. He combined magnesia with sulphuric, 

 nitric, muriatic, and acetic acids, and ascertained tile 

 properties of the salts formed ; compared them with 

 similar salts of lime, and pointed out the essential 

 differences. He determined the efFect of heat upon 

 magnesia ; shewed that it deprived it of a quantity of 

 air ; that the magnesia continued still tasteless and 

 insoluble in water ; that it combines with acids with- 

 out effervescence, and forms with them the very 

 same salt as common magnesia. He determined the; 

 affinity of magnesia for acids, when compared with 

 lime and alkalies ; and pointed out the difference be- 

 tween it and alumina, and the earth of bom;. 



The investigation and determination of the proper- 

 ties of magnesia, though an object of great import. 

 ance, sinks into insignificance when compared with 



BIrcV. 



