On the Protein Question. 163 



which the name of protein is given, and which, according to the ana- 

 lyses hitherto made, may be most nearly represented by the empiri- 

 cal formula, — 



QiQ H25 N^ Oi« + 2 H O. 



The older formula, now abandoned by Mulder, was — 



QiQ HZl ^5 012. 



The latter of these formulse contains a larger proportion of nitro- 

 gen than the one now adopted. This arises from the circumstance 

 tihat a part of the nitrogen supposed formerly to belong to the pro- 

 tein is now found to exist in it in a different state (that of an amid), 

 and not properly to belong to the composition of the pure protein 

 itself. 



2. That this protein combines with the amid of the hypo-sul- 

 phorous, and probably of the hypo-phosphorous acid, and forms com- 

 binations which occur abundantly in nature. Albumen, casein, fibrin, 

 &c., are such natural combinations. The nitrogen of these amids 

 was included in the old formula for protein, and hence, when it is 

 abstracted, the new formula must contain less nitrogen. 



3. That these combinations of protein with the amids, when heated 

 upon a plate of silver, with a few drops of a solution of caustic potash, 

 evolve ammonia and sulphuretted hydrogen ; which last product 

 blackens the surface of the polished silver. 



4. That they also unite directly with the chlorous, the tannic, and 

 other acids, forming combinations of the natural albumen, casein, 

 &c., with these acids. Such a compound with albumen is formed 

 when a solution of tannic acid is poured into an aqueous solution of 

 the white of egg. These compounds all blacken silver under the 

 influence of caustic potash, as the albumen and casein themselves do. 



5. That by the prolonged action of caustic potash, aided by a gentle 

 heat and access of air, the amids contained in these natural com- 

 pounds are decomposed — their nitrogen more or less completely 

 separated in the form of ammonia, and their sulphur converted into 

 sulphurous and phosphorous acids which combine directly with the 

 protein. When separated from the potash by acetic acid, the com- 

 bination obtained contains these two acids in variable proportions, and 

 does not blacken silver when treated as above described. 



The prolonged action of chlorine produces a similar effect — form- 

 ing at first compounds of the chlorous sulphurous and phosphorous 

 acids with protein, which do not blacken silver. 



6. But that by a prolonged action of chlorine under other known 

 circumstances, the proportion of the sulphurous and phosphorous acids 

 in these compounds diminishes, and becomes very variable. Mixtures 

 in fact are obtained in which pure chlorite of protein exists contami- 

 nated with more or less of certain compounds of the same chlorite 

 with the acids of sulphur and phosphorus. 



