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 weigned 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 weigned 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

Railroad are given in an article by Job on Practical Testing and Valuation of Japan:

The material desired consists of a pure turpentine hardener and oil drier, conforming to the following:

1st. When equal parts by weight of the Japan and of pure turpentine are thoroughly mixed and poured over a slab of glass, which is then placed nearly vertical at a temperature of 100 degrees Fahrenheit, with a free access of air but not exposed to draft, the coating shall be hard and dry, neither brittle nor sticky, in not exceeding twelve minutes.

2d. When thoroughly mixed with pure raw linseed oil at the ordinary temperature in proportions of 5 per cent by weight of Japan to 95 per cent by weight of raw linseed oil, no curdling shall result, nor any marked separation or settling on standing.

3d. When the above mixture is flowed over a slab of glass, which is then placed nearly vertical at a temperature of 100 degrees Fahrenheit, with free access to air but not exposed to draft, the coating shall dry throughout, neither brittle nor sticky, in not exceeding two hours.

4th. When five cubic centimeters of the Japan are poured into 95 cubic centimeters of pure turpentine at the ordinary temperature, and thoroughly shaken, a clear solution shall result, without residue, on standing one hour.

5th. After evaporation of the turpentine, the solid residue must be hard and tough, and must not "dust" when scratched with a knife.

6th. Benzin or mineral oil of any kind will not be permitted.

This, with the following specification of the U. S. Navy Department, will furnish a very good basis for an examination of Japan drier:

1. Japan drier must not flash below 105° F. (open tester); must be of the best quality and made from pure kauri gum, pure linseed oil, pure spirits of turpentine, and lead manganese driers, and be free from adulterants and all other foreign materials; must set to touch in from one-fourth to one hour, dry elastic in from 18 to 21 hours at a temperature of 70° F.. and must not rub up or powder under friction by the finger. When mixed with pure raw linseed oil in the proportion of 8 parts of oil to 1 part of drier, must remain clear for two hours and set to touch in from 6 to 7 hours at a temperature of 70° F.

PAINTS.

STRENGTH TEST.

The strength of pigments does not bear a very close relationship to the chemical composition, hence a quantitative analysis does not necessarily give the information actually desired. For this reason the "strength test" is of great importance. A standard color is usually selected, but in case no standard is used all of a series of similar colors may be compared with one another.

Weigh equal portions of the samples to be tested, and, if available, a standard sample; add to each equal portions of pure zinc oxid, the amount depending upon the character of the color tested (this may vary from 5 to 60 times that of the color). Rub up each mixture on a glass plate or, better, a stone slab, until there is no change in shade on further rubbing. Rate the samples in the order of their depth of tint. White pigments may be rated in a similar way by grinding up each with the same colored pigment, such as Venetian red. With yellows use chrome green or Prussian blue instead of a white diluent. Add the same number of drops of raw linseed oil to all samples in grinding for the strength test.

WHITE PIGMENTS.

1. White Lead.

Pure white lead is basic carbonate of lead and should approach the following composition: 2PbCO;Pb (OH) 2. It should be completely soluble in acetic acid. Test for barium and calcium by the flame test. Use an iron wire, as platinum will be ruined by the lead.

a Chemical Engineer, 1906, 4: 198–202.