Tests loith Pt'ecipitins 399 



eliminated in the following way. Solutions of all of the above 

 substances were allowed to stand till the excess had settled to the 

 bottom. Tlic supernatant Huid was then pipetted off and filtered. 

 Carbon dioxide gas generated by the action of dilute hydrochloric acid 

 on chalk, and washed by passing through distilled water, was next 

 passed through the fluid and the latter again filtered to free it from the 

 presence of the precipitated calcium carbonate. By this procedure 

 clear filtrates could be obtained in most cases, which remained so for 

 an indefinite period, and produced no cloudings on the addition of sera. 

 The following formula explains the reaction : 



Ca (OH), + CO, = Ca CO3 + H.,0. 



Too much of the gas must not however be passed into the solution 

 owing to the fact that excess of CO.2 renders the insoluble carbonate 

 again soluble : 



Ca CO3 + H,0 + CO, = Ca H, (COa)^. 



By quantitative experiments it was found that though this process 

 caused a deposition of blood pigment from blood solutions, yet the 

 property of producing precipitation on the addition of appropriate 

 antisera was not in any way affected, 



TJie action of dry and wet lime, etc. 



Lime was intimately mixed with human blood and then spread on 

 porcelain and exposed to the action of air for three months. The 

 resulting compound turned a greenish colour. Solutions of this gave 

 an immediate clouding on the addition of serum. After the passage of 

 CO2, however, and subsequent filtration, no reaction could be obtained 

 with anti-human or other serum. Under these conditions it seems that 

 unslaked lime completely destroys the reacting power of blood in 

 contact with it. 



Quantitative experiments over a shorter period bring out the 

 destructive quality of lime and mortar very markedly. To ascertain 

 the action on serum of dry and wet lime, mortar, brick, earth, etc. 

 weighed quantities of one gramme of each were mixed with 1 c.c. of 

 human serum and allowed to act for 4 days. Similar mixtures but with 

 10 c.c. of water added were also prepared and allowed to stand for 4 

 days, to determine whether any different action was excited by these 

 materials in the presence of water. At the end of this period all were 

 made up to 1 : 21, by the addition in the former case of 20 c.c, of 

 normal, and in the latter of 10 c.c. of double normal salt solution. 



