256 



CHEMICAL MANUEES. 



191 parts of nitrogenous niatter, fibrin, albumen, globulin. 

 A ,, ,, tat. 

 3 ,, ,, extractive. 

 8 ,, ,, mineral matter. 



204 



Amongst the mineral matters of blood, mention must be made of 

 chloride of potassium and of chloride of sodium (common salt), and 

 also phosphoric acid, lime, and magnesia. Phosphoric acid forms 

 9-8 parts ; potassium chloride, 46 parts : corresponding to 29 parts 

 of potassium. The composition of blood differs a little according 

 to the animals from which it comes, as the following analyses by 

 Wolff show^ : — 



TABLE LXXIII.— ANALYSES OF BULLOCKS, CALVES, SHEEP, AND 



PIGS' BLOOD. 



Dried Blood. — Up to now (and still at the present time) blood 

 was mostly coagulated in factories by steam in an open pan, adding 

 to it 3 per cent of ferric sulphate solution marking 51° B. (110° Tw.).. 

 The coagulated blood was then laid to drain in perforated cases, 

 where it remained for a month, and thus lost 40 per cent of the 

 80 per cent of the w^ater which it contained. The coagulated and 

 drained product was then dried on hot cast-iron plates in a shelf- 

 oven traversed by hot gases. This mode of operating has numerous 

 drawbacks ; odoriferous fumes are given off by the drying itself and 

 bad-smelling fumes owing to the partial decomposition due tO' 

 irregular heating of the nitrogenous matter. Attempts have been 

 made to remedy this, it is true, by condensing the first and de- 

 naturing the second by fire. 



Moreover, not only do the arrangements necessary to secure a 

 satisfactory result require continuous supervision, but the manu- 

 facturer does not apply them except against his will, as they per- 

 ceptibly increase the cost of the products without any marked 

 advantage as regards quality. The drying of blood in Donard and 

 Boulet's machine — about to be described — prevents the disengage- 



