460 APPENDIX. 



gradually added to a mixture of 3 litres [5 '3 pints] of water and 

 1300 grammes of sulphuric acid, which must be previously raised 

 to the boiling point ; and the whole must be kept boiling for forty- 

 eight hours ; after dilution with much water and neutralisation 

 with milk of lime, we treat the filtrate with a little more milk of 

 lime and allow it to boil for an hour or two in order to decolorise 

 it ; the fluid, after filtration, is then evaporated to 2 litres, a stream 

 of carbonic acid being passed continuously through it during the 

 process ; on being again filtered and allowed to stand the tyrosine 

 separates in crystals. Leyer and Roller employ the following 

 method : they boil 1 part of protein-substance with 4 parts of sul- 

 phuric acid and 12 parts of water for forty hours; the brown fluid 

 is rendered alkaline by milk of lime, and is again heated and filtered. 

 Sufficient sulphuric acid is then added to nearly destroy the alka- 

 line reaction ; the tyrosine now crystallises in tolerable purity from 

 the evaporated filtrate. 



With regard to testing for tyrosine, when its quantity is not 

 sufficient to enable us to recognise its presence from its properties, 

 and by its analysis, Piria recommends the employment of the 

 reaction of the salts of tyrosine-sulphuric acid with neutral 

 perchloride of iron, when a dark violet colour is manifested. If 

 we place a little tyrosine (a few millegrammes are sufficient) in a 

 watch-glass, moisten it with 1 or 2 drops of sulphuric acid, dilute 

 it after half-an-hour with water, saturate it when heated with 

 carbonate of lime, and add perchloride of iron (without any free 

 acid) to the filtered fluid, the presence of tyrosine is indicated by 

 the appearance of a dark violet colour. G. E. D.] 



(14.) Addition top. 163, line 24. Scherer*has obtained much 

 more correct results than Becquerel in the case of children and 

 adults. He found that the urine of young children contained on 

 an average 1'7-jj- of urea, while he found only 1'25-g- in the 24 hours 3 

 urine of a young man aged 22 years. Determinations of this 

 kind lead, however, to few conclusions; to obtain an insight into 

 the general process, our determinations should have reference to 

 definite intervals of time, and to definite weights. A boy aged 3| 

 years discharged in 24 hours 12-98 grammes of urea; a girl aged 

 7 years, 18'29 grammes; a youth aged 22 years, 37*008 grammes, 

 and a man aged 38 years, 29'824 grammes. If, however, we take 

 the relative weights into consideration, it follows that for 1 kilo- 

 gramme's weight of the child there was discharged 0'810 of a 

 * Verh. d. phys.-med. Ges. z. Wurzburg. Bd. 3, S. 180-190. 



