In calculating the percentage of rosin, assume the iodin number for pure rosin to be 228, that for pure unbleached shellac to be 18, and for pure bleached shellac, 10. These figures will tend to give somewhat low results on rosin percentage, but should be used, as it is then safe to say that there is at least as much rosin present as is found by analysis. 3. Alcohol Insoluble. Add to 1 gram of shellac 60 cc of 95 per cent alcohol, heat to boiling, and filter on a Gooch crucible; wash with about 60 cc of boiling 95 per cent alcohol, dry at 100° C. and weigh. 4. Loss on Drying-Water. Heat 1 gram for two hours in a water oven at 100° C. culated as water. Loss in weight is cal 5. Ash. Determine ash on 1 gram, heating only to dull redness. SHELLAC IN ALCOHOL. 1. Total Solids and Ash. Evaporate 1 gram of the varnish in a porcelain dish on the water bath and dry to constant weight in steam oven (about five hours). Ash residue as in dry shellac. 2. Examination of Solvent. Note the odor of the varnish, as little can be learned from the odor of the distillate. Distil 100 grams of the varnish until incipient decomposition begins; redistil the distillate, noting the boiling point, and determine the specific grav-. ity of the distillate. By this means it is usually an easy matter to determine whether the varnish is made with wood alcohol, grain alcohol, or denatured alcohol. Dilute a portion with three times its volume of water; if benzin is present it will separate. 3. Test for Rosin. Do not use the residue from the total solids determination, but carefully weigh in a capsule a quantity of varnish sufficient to yield 0.2 gram of solid material, evaporate to a paste, and treat the residue as described under "dry shellac," paragraphs 1 and 2, page 16. DAMAR VARNISH. Damar varnish, which should be a solution of damar gum in spirits of turpentine, is examined by the methods for oil varnishes (page 18). The percentage and nature of the volatile oil, specific gravity, and flash point are important tests. It should yield little ash, which should contain no lead or manganese. When flowed on glass it should set to touch in a very short time (less than thirty minutes) and mixed with zinc white should yield a good white enamel surface when applied to wood. In testing for rosin by the Liebermann-Storch test (page 19), the light claret color characteristic of damar should not be mistaken for the violet color char 20470-Bull. 109-10-3 acteristic of rosin. The Hirschsohn test for rosin, which is less delicate than the Liebermann-Storch method, is as follows: Digest about 1 gram of the dried resin with approximately 20 cc of ammonium hydroxid for twenty minutes, filter and acidify with acetic acid. With pure damar the liquid remains clear, but if rosin is present a precipitate forms, and when the proportion of rosin is large the entire acid liquid may become gelatinous. The acid number of damar is lower than that of rosin and higher than that of the hard varnish gums. An oil varnish made of hard gums will generally have an acid number of less than 12. A damar varnish will have an acid number between 15 and 20, a higher number generally indicating the presence of rosin. OIL VARNISH. The methods of analysis for varnish are far from satisfactory. A number of methods for determining the amount of gums in varnish have been proposed, but none of them are reliable. This determination, therefore, is not made, but the combined percentage of oil and gums is reported. 1. Appearance and Odor. Transfer the sample if it is in a metal container to a glass-stoppered cylinder or bottle and note its appearance, color, transparency, body, and whether any sediment is deposited. The presence of light petroleum oil or wood turpentine may often be detected by noting the odor of the sample. After making these observations, the sample should be thoroughly mixed before making the remaining tests. 2. Specific Gravity. Determine with a pyknometer, plummet, or hydrometer at 15.5° C. 3. Flash Point. Determine as in spirits of turpentine; but begin testing at 25° C. and stir the varnish while heating. A low flash point indicates light petroleum oil. 4. Viscosity. The determination of viscosity is seldom necessary; but if desired, make the determination by the Engler-Ubbelohde method at 20° C. 5. Volatile Oils. Weigh 100 grams of the varnish into a 500 cc flask, connect with a spray trap and a vertical condenser, and pass through it a current of steam, first heating the flask in an oil bath at 100° C.; with the steam still passing through, raise the temperature of the bath to 130° C. Catch the distillate in a small weighed separatory funnel; continue distillation until 300 cc of water has been condensed. Portions of this water may be drawn from the cock of the separatory funnel from time to time, but care must be taken not to draw out any of the volatile oil. Let the distillate stand until it separates into two layers, then draw off the water and weigh light oils. Filter the light oils through dry paper and examine as directed under spirits of turpentine (page 13). A slight error is caused by the solubility of turpentine in water; this amounts to about 0.3 to 0.4 ce for each 100 cc of water. When sufficient varnish is available, it is well to take another portion and distil, without steam or spray trap, placing the weighed flask in an oil bath. Note the temperature of the bath at which distillation begins, and continue distillation at a temperature of 185° C. in the oil bath, finally raising the temperature to 200° C. This method generally tends to give lower results on volatile oils than the steam distillation method; but the distillate can be tested for watersoluble volatile liquids, which would be lost by the steam distillation. 6. Fixed Oil and Gums. The percentage of fixed oil and gums is obtained by subtracting the percentage of volatile oils from 100. A check upon this determination is obtained by weighing the residue from the dry distillation. 7. Acid Number. Determine the acid number in the usual way, using 10 grams of varnish. 8. Rosin. After getting the acid number, decant the alcohol, evaporate, and apply the Liebermann-Storch test for rosin (page 16). 9. Ash. Determine the ash in 10 grams, using a quartz or porcelain dish and carrying out the determinations at a low heat, best in the muffle. Determine the reaction of the ash to litmus paper and make a qualitative analysis. It is frequently well to make a quantitative determination of lime, a large amount of which indicates rosin. It is sometimes advisable to determine the percentage of lead and manganese. Some lead will, however, be lost in the ashing, and if a correct lead determination is required, follow the method described for mixed paint vehicles (page 41). 10. Miscellaneous. It is not possible from such an examination as has just been described to decide on the value of a varnish for any particular purpose, though valuable information as to the materials used in its manufacture may be obtained. An examination of the varnish film should, therefore, always be made. The films are best made by flowing the varnish on carefully cleaned plates of glass, and allowing to dry at room temperature in a vertical position. Observe the time of setting and the nature of the film after twenty-four hours, noting the transparency, hardness, elasticity, tendency to dust by scratching, etc. After thorough drying, immerse the plate in water over night, dry, and note appearance. The working quality of a varnish must be determined by application on wood, and it is best to make this test on well seasoned and perfectly smooth white pine. Apply a thin coat of the varnish to wood and allow to dry, sandpaper down smooth, and then apply the coat to be tested. Observe how the varnish works under the brush, character of coat, etc. This panel, after drying, may be used for further testing as to whether the varnish will stand rubbing, etc. JAPAN DRIER. The analysis of Japan drier is conducted in the same way as that of varnish. The following specifications for Japan drier for the Philadelphia and Reading acteristic of rosin. The Hirschsohn test for rosin, which is less delicate than the Liebermann-Storch method, is as follows: Digest about 1 gram of the dried resin with approximately 20 cc of ammonium hydroxid for twenty minutes, filter and acidify with acetic acid. With pure damar the liquid remains clear, but if rosin is present a precipitate forms, and when the proportion of rosin is large the entire acid liquid may become gelatinous. The acid number of damar is lower than that of rosin and higher than that of the hard varnish gums. An oil varnish made of hard gums will generally have an acid number of less than 12. A damar varnish will have an acid number between 15 and 20, a higher number generally indicating the presence of rosin. OIL VARNISH. The methods of analysis for varnish are far from satisfactory. A number of methods for determining the amount of gums in varnish have been proposed, but none of them are reliable. This determination, therefore, is not made, but the combined percentage of oil and gums is reported. 1. Appearance and Odor. Transfer the sample if it is in a metal container to a glass-stoppered cylinder or bottle and note its appearance, color, transparency, body, and whether any sediment is deposited. The presence of light petroleum oil or wood turpentine may often be detected by noting the odor of the sample. After making these observations, the sample should be thoroughly mixed before making the remaining tests. 2. Specific Gravity. Determine with a pyknometer, plummet, or hydrometer at 15.5° C. 3. Flash Point. Determine as in spirits of turpentine; but begin testing at 25° C. and stir the varnish while heating. A low flash point indicates light petroleum oil. 4. Viscosity. The determination of viscosity is seldom necessary; but if desired, make the determination by the Engler-Ubbelohde method at 20° C. 5. Volatile Oils. Weigh 100 grams of the varnish into a 500 cc flask, connect with a spray trap and a vertical condenser, and pass through it a current of steam, first heating the flask in an oil bath at 100° C.; with the steam still passing through, raise the temperature of the bath to 130° C. Catch the distillate in a small weighed separatory funnel; continue distillation until 300 cc of water has been condensed. Portions of this water may be drawn from the cock of the separatory funnel from time to time, but care must be taken not to draw out any of the volatile oil. Let the distillate stand until it separates into two layers, then draw off the water and weigh light oils. Filter the light oils through dry paper and examine as directed under spirits of turpentine (page 13). A slight error is caused by the solubility of turpentine in water; this amounts to about 0.3 to 0.4 cc for each 100 cc of water. When sufficient varnish is available, it is well to take another portion and distil, without steam or spray trap, placing the weighed flask in an oil bath. Note the temperature of the bath at which distillation begins, and continue distillation at a temperature of 185° C. in the oil bath, finally raising the temperature to 200° C. This method generally tends to give lower results on volatile oils than the steam distillation method; but the distillate can be tested for watersoluble volatile liquids, which would be lost by the steam distillation. 6. Fixed Oil and Gums. The percentage of fixed oil and gums is obtained by subtracting the percentage of volatile oils from 100. A check upon this determination is obtained by weighing the residue from the dry distillation. 7. Acid Number. Determine the acid number in the usual way, using 10 grams of varnish. 8. Rosin. After getting the acid number, decant the alcohol, evaporate, and apply the Liebermann-Storch test for rosin (page 16). 9. Ash. Determine the ash in 10 grams, using a quartz or porcelain dish and carrying out the determinations at a low heat, best in the muffle. Determine the reaction of the ash to litmus paper and make a qualitative analysis. It is frequently well to make a quantitative determination of lime, a large amount of which indicates rosin. It is sometimes advisable to determine the percentage of lead and manganese. Some lead will, however, be lost in the ashing, and if a correct lead determination is required, follow the method described for mixed paint vehicles (page 41). 10. Miscellaneous. It is not possible from such an examination as has just been described to decide on the value of a varnish for any particular purpose, though valuable information as to the materials used in its manufacture may be obtained. An examination of the varnish film should, therefore, always be made. The films are best made by flowing the varnish on carefully cleaned plates of glass, and allowing to dry at room temperature in a vertical position. Observe the time of setting and the nature of the film after twenty-four hours, noting the transparency, hardness, elasticity, tendency to dust by scratching, etc. After thorough drying, immerse the plate in water over night, dry, and note appearance. The working quality of a varnish must be determined by application on wood, and it is best to make this test on well seasoned and perfectly smooth white pine. Apply a thin coat of the varnish to wood and allow to dry, sandpaper down smooth, and then apply the coat to be tested. Observe how the varnish works under the brush, character of coat, etc. This panel, after drying, may be used for further testing as to whether the varnish will stand rubbing, etc. JAPAN DRIER. The analysis of Japan drier is conducted in the same way as that of varnish. The following specifications for Japan drier for the Philadelphia and Reading |