123 
Evidently the NaCl has not affected the volume of BaSO,. 
A similar result was obtained when Na,HPO, 12 aq. was added, 
(See table III p. 122). 
Where the precipitate has not been polluted, the volume of BaSO, 
has obviously not been modified by the phosphate. 
Finally an experiment to investigate the influence of the salts met 
with in animal substances. 
TABLE IV. 
Effect of a mixture of K, Na, Mg, Cl and Na,HPO, on the volume of the precipitate. 
7,5 cc. of HCI sulphate solution +5 cc. of BaCl. solution containing acetone. of Baso, 
1) 2cc. of NasSO, 40/, + 214 cc. of HCI1:1 + 3ece. of H,0 81.5 
2) 2 ” si 21g fi ” = 3 ” 80.5 
3) 2 cc. of NasSO, 49/9+- 214cc.0f HCI: 1+1,2eC.of KCI3,60/9+0,8eC.of NaC190/, 
_ + 1,3 ec. Na,HPO, 90/, + 0,8 cc. CaCl, 3’, 
+ 0,8 cc. MgClo 20’ + 0,2 cc. HaO 82.5 1) 
4) like 3 82.5 1) 
From this experiment it may be concluded that if the foregoing 
prescriptions (sub 3) are carried out, the volumetrical sulphate- 
determination gives highly satisfactory results, much more so than 
the gravimetric method. But we repeat on the ground of our exten- 
sive researches that the directions must be carefully attended to. 
The prescriptions especially apply to the manner in which fluid 
and reagent are mixed. The size and shape of the crystals depend 
on it. Hence we are in the habit, when the mixture has taken place, 
of taking a drop of the turbid fluid with a capillary pipette and 
examine it under the microscope (Leitz obj. 8, Oc. 2). It becomes 
then evident at once without measurement whether the crystals are 
right. As we said before they suggest small cubes. Their surface 
must seem smooth. If the microscopic view does not. satisfy this 
demand, if the crystals seem rough at the surface or if they have 
for. instance double the diameter then the volume of the sediment 
is also found to exceed 51.5 divisions. Who has not yet seen the 
desired crystals may take as a criterion whether 2 c.c. Na,SO, 10 
aq. of 4°/ gave a volume of 81.5 divisions. Whenever this was the 
case, the crystals were as they should be. A preparation may be 
kept to serve for comparison. When kept, evaporation must of 
1) The Kek had lost some small particles, which polluted the column of BaSQ,. 
