366 Letter from Professor Mulder. 



cation. The question is simply, What is the truth ? and the answer 

 to this is : " Albumen, fibrin, casein, &c., can be freed from sulphur 

 by potash alone ; that is, they can be deprived of that reaction which 

 we in science distinguish as characteristic of the presence of sulphur." 

 Sulphuret of calcium we call desulphuretted, when it yields no longer 

 a black precipitate with acetate of lead. When it is totally con- 

 verted into gypsum, we still call it desulphuretted (outzwaveld), al- 

 though we find in it sulphuric acid. 



Leibig has, in a covert manner, by a play of words, shifted and 

 mutilated the original sulphur question. It is true, that I have 

 stated in my last experiments, that protein, when burned with nitre, 

 yields no sulphuric acid, or only traces of it, but the true state of 

 the sulphur question is this : Does the reaction on silver or on acetate 

 of lead disappear ? 



I must draw your attention to this, because it is of importance for 

 the sake of science. And it is of importance for science, because its 

 only object is truth, and not to decide, who is right or wrong. 



As I am disgusted with this mutilation, I would really have de- 

 clined taking up the pen to expose it, had not the observation, that 

 protein, on being burned with nitre, produces a weighable quantity 

 of sulphuric acid, again forced my attention upon the entire protein 

 question. 



I can mention to you, as the result of my investigations, that the 

 sulphur exists in albumen, horse and cow hoofs, &c., in the state of 

 sulphuret of amid (S, N H^) ; that protein from albumen contains 

 variable traces of hyposulphurous acid, S^ O'^, in weighable quantities ; 

 that this hyposulphurous acid is a product of the decomposition of 

 two equivalents of sulphuret of amid 2 (S, N H^), which, by the in- 

 fluence of alkali and two equivalents of water (2 H 0), produce an 

 equivalent of hyposulphurous acid, and two equivalents of ammonia 

 (S^ 0^ and 2 N H^) ; that, therefore, protein yields variable quan- 

 tities of hyposulphurous acid, and consequently contains the sulphur 

 under a form which has nothing in common with that in which it 

 originally existed ; — that cow-horns and fibrin consist of sulphuret 

 of amid (S, N H^) with a body differing from protein only in the 

 proportion of oxygen ; — that protein from fibrin contains only 1 per 

 cent, of hyposulphurous acid, being a quantity which, in the ultimate 

 analysis, has no perceptible influence on the proportions of carbon, 

 hydrogen, and oxygen ; — that the quantity of hyposulphurous acid 

 in protein from albumen may rise to 2-66 per cent., but is not con- 

 stant ; that this quantity may arbitrarily be diminished or increased, 

 but, — and here I beg to correct a mistake, which I committed in my 

 last experiments, and which I therefore clearly and distinctly ac- 

 knowledge, — ^that hitherto I have been equally unable to remove 

 from protein the last traces of hyposulphurous acid, as to separate 

 from it the last traces of incombustible substances. 



But does this imply that protein, — protein free /rom sulfhur, — has 



