IGi Professor Mulder 



Thus far at present — irrospoctivo of personal contentions — our 

 groping after the truth seems to carry us. — Believe nie, yours very 

 truly, 



James F. W. Johnston, 

 To Professor Jameson, Edinburgh. 



Utrecht, 27th May 1847. 



My Dear Friend, — The albuminous bodies about which I wrote 

 you some time ago, required a detailed investigation, in consequence 

 of what I had discovered, namely, that the sulphur and phosphorus they 

 contain, exists in the state of sulphamid and phosphamid, and that 

 hyposulphurous acid is present in the precipitate produced by dis- 

 solving them in caustic potash, by the aid of heat, and adding acetic 

 acid in excess. 



I have, without intermission, continued my investigations, and 

 the result is, that the above named constitution is common to them 

 all. Hair, whalebone, casein, legumin, albumen, fibrin, horny mat- 

 ter and the nails, consist of nothing else than the above amids, com- 

 bined in different proportions, either with protein, or with an organic 

 group, which can bear no other name than that of oxide of protein. 

 I formerly gave you instances of this in the composition of fibrin, 

 horn, and legumin. 



It is evident, after this discovery, that the empirical formula, 

 by which we have hitherto represented protein, ought to receive 

 some modification. All my former results tend to corroborate this, 

 and you will find, that all that is necessary is a change of names, 

 and tbat the results of my former analyses remain unaffected. It 

 was wrong, therefore, to attempt to throw suspicion upon my results. 

 Only, what I formerly called chlorite of protein, must receive the 

 name of chlorite of albumen, of casein, and of fibrin, and if you 

 change these names, then everything else remains the same. What 

 I formerly distinguished by the name of sulpho-proteic acid,Jought to 

 be called sulphate of albumen, or of casein, but the analytical results 

 stand unaltered. 



It is only by my present investigations that I have become ac- 

 quainted with chlorite and sulphate of protein. In composition and 

 properties, they very much resemble the combinations of chlorous and 

 sulphuric acid, with albumen, casein, &c. ; but when heated with 

 potash upon a silver plate, they do not produce a black spot. They — 

 the chlorites, that is to say — all contain a small quantity of hyposul- 

 phurous acid ; but, in some compounds, which otherwise are pure 

 chlorites of protein, this hyposulphurous acid does not amount to 

 more than 0*6 per cent. They thus prove, that this hyposulphurous 

 acid, of which very variable quantities may also exist in protein, is 

 not an essential ingredient of it ; and, further, that notwithstanding 

 all the trouble that is taken now to direct attention to this sulphur, 

 it will be an unsuccessful attempt to deny the existence of an inde- 



