41 



141. Series of specimens illustrating the chemical 

 transformations of uric acid. 



E. 7 to 12. 1887. Prepared by Dr. SchucliawU, Gorlitz. 



Allantoin. 



Alloxan. 



Alloxantin. 



Hydantoin. 

 Parabanic acid. 

 Biuret. 



2. APPARATUS AND SPECIMENS ILLUSTRATING 

 THE APPLICATION OF CHEMISTRY TO THE 

 ARTS AND MANUFACTURES. 



A. CHEMICALS EMPLOYED IN OR RESULTING FROM VARIOUS 

 MANUFACTURES AND MODELS TO ILLUSTRATE METHODS OF 

 PRODUCTION. 



142. Model of sulphuric acid works. 



E. 8. 1890. Made ly B. L. F. Potts. 



A complete plant for the manufacture of sulphuric acid is 

 represented on a scale of ^ inch to the foot. 



On the left are a set of 18 pyrites burners placed in two rows 

 back to back ; here the sulphur of the pyrites is burnt, sulphur 

 dioxide being formed by its combustion. Before burning, the 

 pyrites is broken up into convenient sizes by the crushing- 

 machine placed before the burners. 



The hot gases from the burners pass over sets of nitre pots, 

 where nitric acid is disengaged by the action of sulphuric acid 

 on Chili saltpetre (sodium nitrate), and then into a large cham- 

 ber whence they pass into the base of the circular Glover's tower 

 (30 ft. high, 9 ft. diameter). 



In this tower the hot gases come first into contact with com- 

 paratively weak acid, which suffers loss of a portion of its 

 water, and so becomes sufficiently concentrated to be used in the 

 Gay-Lussac's tower, as indicated below ; as the still hot gases 

 pass up through the packing of the tower they meet neir the 

 top the mixture of nitrous vitriol (from the base of the Gay- 

 Lussac's tower) and chamber acid ; this diluted nitrous acid, by 

 the combined action of the heat and the sulphur dioxide, is 

 deprived of the nitrogen oxides held in solution. 



The fumes here liberated pass on to the chambers along with 

 the burner gases (sulphur dioxide, oxygen, and nitrogen), and 

 the nitrogen fumes from the nitre pots. 



The distribution of the nitrous vitriol and chamber acid at 

 the head of the Glover's tower is accomplished by means of a 



