8 
COMPARATIVE EXPERIMENTS ON THE EFFECT OF 
crude bone dust, and 0.157 %, the lowest content, in the 
crop produced with steamed bone dust. Although the difference 
between these figures is not great, it affects considerably the 
results calculated for the relative assimilability. By the way, we 
may point out in this place that the proportion of phosphoric 
acid in the barley crop, in the average of the above figures 0.172 
°/o of the dry matter, almost coincides with that (0.168 %) in 
paddy rice (straw and grain). 
With reference to the mammal value of the various forms of 
phosphoric acid our experiments have shown that on dry land the 
first rank must be awarded to the superphosphate, of the phosphoric 
acid of which 21.5 % was recovered in the crop. Owing to its 
richness in sesquioxides of iron and aluminium our soil is not 
particu’arly favorable to the action of this manure, as the soluble 
phosphate if applied in the autumn is sure to be converted during 
the winter, to a comparatively large extent, into basic compounds 
which are less available to the roots.—Next in value comes the 
steamed bone dust which yielded 16,6 % of its phosphoric acid to 
the crop, and which approaches, in its effect (79), very near to 
that of the superphosphate (100). This result is about eight times 
that (10) obtained by P. Wagner in his comparative experiments, 
and shows that, under favorable climatic conditions, the steamed 
bone dust is one of the best kinds of concentrated commercial 
fertilizers. The effect displayed by it in our experiments must 
not be even regarded as a maximum attainable only under excep¬ 
tionally favorable conditions, because our specimen of bone dust 
was not of the best kind but of rather inferior quality owing to the 
partial extraction of gelatinoid (see p. 3).—The precipitated 
calcium phosphate which ranks next to the steamed bone dust and 
of the phosphoric acid of which only 13.8 % was consumed by the 
crop, is likewise an excellent phosphatic manure, and according 
to other observers, frequently has a still better action than in our 
experiments.—The crude bone dust and raw cm shed bones which 
differed from each other in the size of the particles and in their 
content of fat—the former containing only 1.93, the latter r4.o7 %, 
were nevertheless consumed to the same extent (12.4 resp. 12.6 %) 
