44 Dr. Serturner on the Combination of Acids [Jui.Y, 



platinum and gold) whose bases are not in a state to be separated 

 without the assistance of another body, perhaps of a compound 

 of oxvsen, as oxvgen gas, water, &c. are compounds containing 

 a third body, which owes its presence to this. 



I now return again to the combinations of acids with acids and 

 indifferent substances. What is already known respecting these 

 combinations, we owe chiefly to the valuable labours of Chevreul; 

 Thenard, and some other modern chemists ; but the facts which 

 they have stated do not consist in direct combinations of these 

 bodies, but of what may be called combinations of the fragments 

 of their constituents. The same observation applies to the 

 valuable researches of Bauhoff on the relation of alcohol to 

 oxalic acid. They have not to do with alcoholic acids, the 

 compounds which I propose to describe ; but with compounds 

 of the fragments of organic bodies with acids, which are formed 

 only by difficult processes. 



Appendix concerning Alcoholic Acids, and Acid Compounds 

 derived from the Union of strong Acids with indifferent Sub- 

 stances. 



The preceding essay gives the method, very briefly indeed, but 

 clearly, of forming the new acids with a double base ; but I 

 consider it as still necessary to add some observations on the 

 method of preparing these acids, and of the precautions which 

 are requsite in order to ensure success, though the manner of 

 forming them all is in some respects the same, yet every one 

 requires some steps which are peculiar to itself. When muriatic 

 acid is employed, the water requires to be removed by means of 

 sulphuric acid, or, still better, by means of nitric acid and 

 chlorine. 



Protoinothionic Acid. 



Two volumes of absolute or very strong alcohol are to be mixed 

 with one volume of concentrated smoking sulphuric acid. The 

 alcohol and sulphuric acid let water and heat escape at the same 

 time, and unite together, constituting protoinothionic acid. It 

 is now to be heated, and to be slowly saturated with chalk, after 

 having been previously diluted. A little gypsum is formed 

 which is separated from the liquid by filtration through fine linen 

 and washing with water. The liquid is now gently evaporated 

 with a small addition of chalk ; and as soon as a crust begins 

 to appear on the surface, it is filtered while still hot. On cool- 

 ing, protoinothionate of lime separates in soft plates. This salt 

 possesses a peculiar acrid taste, attracts moisture from the 

 atmosphere, takes fire when held in the flame of a candle, but is 

 a permanent salt at the ordinary temperature of the air. When 

 strongly heated, it becomes black, and exceedingly sour. This 

 circumstance deserves attention, because it seems to be the 

 chief reason why this acid, upon which so many persons have 

 been employed in making experiments, was not sooner disco- 

 vered. 



