By isolating monoeter and diether produced in the preparation of bilirubindimethylester from crystalline bilirubin with the use of diazomethane, the author studied the techniques of such isolation as well as the spectroscopic and chemical properties of these ethers, and obtained the following results. 1. For the isolation of monoether and diether by means of the column chromatography active alumina is most suitable as the adsorbent and chloroform is the best developer. 2. By drawing the infrared absorption curve of bilirubindimethylester and its monoether and diether isolated by the above techniques, our on the chemical structural patterns of these substances has been confirmed to be rational. 3. Bilirubindimethylester in the form of a chloroform solution has the maximum absorption at 400mμ, and both monoether and diether have the maximum at 420mμ, showing hardly any difference among these compounds. 4. With the use of organic solvents such as chloroform, petrolether, ethylacetate, and ethylether, bilirubindimethylester is positive to the direct diazo reaction while monoether and diether prove to be negative. 5. Azo dye in the methanol solution of monoether or diether has the maximum absorption at 550mμ, and acidic azo dye by laoding hydrochloric acid to the solution has the maximum absorption at 570mμ. 6. The azo dye obtained by means of direct diazo reaction with monether and diether of bilirubindimethylester gradually moves towards the long side of short wave with the lapse of time, and the peak of the absorption curve becomes flat. However, the maximum absorption of the acidic azo dye produced by loading hydrochloric acid does not change but remain constant. 7. Monoether and diether of bilirubindimethylesteter are both readily soluble in various organic solvents, but with exception of conc. hydrochloric acid and conc. sulfuric acid, they are soluble neither in acids or alklies. 8. In the observations of changes in the color tone monoether and diether in the form of a chlorform solution, taking Gmelin reaction of bilirubin chloroform solution as the control, each shows some differences in the color tone between the case loaded with cone. ferrous chloride aqueous solution and the case loaded with aldehyde reagent. This seems to be dependent upon the stability of each structural pattern.