688 ANNUAL REPORT OP THE Off. DoC. 



fertilizer. The microscope shows clearly the structure of raw bone, 

 but does not make it possible to discriminate between thoroughly 

 acidulaled bone and acidulated ruck. The ratio of nitrogen to phos- 

 phoric acid in a raw bone — and only such bone as has not been 

 deprived of any considerable proportion of its nitrogenous material 

 by some manufacturing process can properly be called "pure animal 

 bone" — is about 1:8; in cases where the ratio of phosphoric acid to 

 nitrogen exceeds 8, it is clear that part, at least, of the phosphoric 

 acid has been supplied by something else than pure animal bone; 

 but, inasmuch as nitrogen may have been introduced in some ma- 

 terial other than bone and no longer detectible by the microscope, 

 the presence of nitrogen and phosphoric acid in the proportions cor- 

 responding to those of bone is not proof positive that they have been 

 supplied by bone. Finally, the difference in the iron and silica con- 

 tent of bone and rock respectively, afford means of distinction use- 

 ful in some cases; the usefulness of this distinction is limited, how- 

 ever, by the facts that kitchen bone frequently contains earthly im- 

 purities rich in iron and silica, and that earthy fillers can legally 

 be used in fertilizers and are in fact considerably used therein both 

 as "make-weights" and as "conditioners," or materials introduced to 

 improve the drilling qualities of the goods. The fact that the phos- 

 phoric acid in bone and rock are identical in character is probably 

 so well known as to require no detailed consideration of the fact in 

 this connection. 



The law having required the manufacturer to guarantee the amount 

 of certain valuable ingredients present in any brand he may put 

 upon the market, chemical analysis is employed to verify the guaran- 

 ties stamped upon the fertilizer sacks. It has, therefore, been deemed 

 desirable in this report to enter the guaranty filed by the manufac- 

 turer in the office of the Secretary of Agriculture, in such connection 

 with the analytical results that the two may be compared. An un- 

 fortunate practice has grown up among manufacturers of so wording 

 the guaranty that it seems to declare the presence in the goods of an 

 amount of a valuable constituent ranging from a certain minimum 

 to a much higher maximum; thus, "Potash, 2 to 4 per cent." is a 

 guaranty not infrequently- given. In reality, the sole guaranty is for 

 2 per cent. The guaranteed amounts given for each brand in the 

 following tables, are copied from the guaranties filed by the maker 

 of the goods with the Secretary of Agriculture, the lowest figure 

 given for any constituent being considered to be the amount guar- 

 anteed. For compactness and because no essentially important fact 

 is suppressed thereby, the guaranties for soluble and reverted phos- 

 phoric acid have not been given separately, but are combined into a 

 single guaranty for available phosphoric acid ; in cases where the 

 maker's guaranty does not specifically mention available phosphoric 

 acid, the sum of the lowest figures given by him for soluble and re- 

 verted phosphoric acid is used. The law of 1879 allowed the maker 

 to express his guaranty for nitrogen either in terms of that element 

 or in terms of the ammonia equivalent thereto; since ammonia is 

 composed of three parts of hydrogen and fourteen parts of nitrogen, 

 it is a very simple matter to calculate the amount of one, when the 

 amount of the other is given; the amount of nitrogen multiplied by 

 1.214 will give the corresponding amount of ammonia, and the amount 



