----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.2026 | 0.7247 | 0.4135 | 0.3583 Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 | 4.5 | 8.03 | 7.04 | 6.67 | 2 | 4.8 | 7.48 | 7.16 | 5.61 | 3 | 4.8 | 6.68 | 6.62 | 4.85 | 4 | 5.1 | 6.00 | 6.24 | 4.65 | 5 | 8.6 | 5.65 | 5.78 | 4.37 | 6 | 8.7 | -- | -- | 4.71 | 7 | -- | 4.85 | 3.72 | -- | 8 | 8.1 | 5.09 | -- | 4.57 | 9 | -- | 4.95 | 2.08 | -- Percentage | 10 | 7.9 | 4.80 | -- | 2.97 Increase | 11 | -- | -- | 1.72 | -- in Weight, | 12 | 8.0 | -- | -- | 3.11 in Days. | 13 | -- | -- | 2.52 | -- | 14 | 8.0 | -- | -- | 3.39 | 15 | -- | -- | 2.35 | -- | 16 | 8.1 | -- | -- | 3.39 | 17 | -- | -- | -- | -- | 18 | 8.0 | -- | 2.32 | -- | 19 | -- | -- | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Film showed | | |Slightly |very little | | |tacky, end |hardening | | |10th and 38th |and remained| | |days.

|soft and | | | |tacky. | | | ----------------+------------+-----------+-----------+--------------

(_b_) COTTON SEED OIL 20 PER CENT.

RAW LINSEED OIL 80 PER CENT.

----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.1516 | 0.9498 | 0.6160 | 0.2553 Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 | 8.5 | 11.00 | 10.94 | 11.83 | 2 | 8.7 | 11.15 | 10.81 | 11.83 | 3 | 9.1 | 10.58 | 10.51 | 10.15 | 4 | 10.8 | 10.17 | 10.37 | 9.29 | 5 | 11.9 | 9.82 | 9.87 | 9.29 | 6 | 11.8 | -- | -- | 9.45 | 7 | -- | 9.02 | 8.93 | -- | 8 | 11.9 | 9.42 | -- | 10.00 | 9 | -- | 9.35 | 8.90 | -- Percentage | 10 | 11.9 | 9.27 | -- | 8.95 Increase | 11 | -- | -- | 8.70 | -- in Weight, | 12 | 11.8 | 9.32 | -- | 8.06 in Days. | 13 | -- | -- | 9.29 | -- | 14 | 11.8 | -- | -- | 8.61 | 15 | -- | 8.81 | 9.63 | -- | 16 | 11.8 | -- | -- | -- | 17 | -- | 8.24 | -- | -- | 18 | 10.7 | -- | 8.47 | -- | 19 | -- | 7.92 | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Fair drying | | |Tacky on 1st |observed at | | |and 2d days.

|end of 4th | | |Dry on 10th |day. Film | | |day.

|slightly | | | |tacky at end| | | |of test. | | | ----------------+------------+-----------+-----------+--------------

TABLE X.--(_a_) SUN FLOWER OIL 100 PER CENT.

----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.1414 | 0.6292 | 0.5837 | 0.2540 Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 | 6.3 | 9.69 | 7.85 | 8.39 | 2 | 8.2 | 9.42 | 7.73 | 6.94 | 3 | 11.5 | 7.99 | 7.45 | 6.21 | 4 | 11.6 | 7.43 | 7.02 | 6.13 | 5 | 11.5 | 7.04 | 6.36 | 5.81 | 6 | 11.5 | -- | -- | 6.01 | 7 | -- | 6.12 | 5.16 | -- | 8 | 11.3 | 6.45 | -- | 6.09 | 9 | -- | 6.12 | 4.57 | -- Percentage | 10 | 11.3 | 5.92 | -- | 4.81 Increase | 11 | -- | -- | 4.20 | -- in Weight, | 12 | 11.3 | 5.69 | -- | 4.73 in Days. | 13 | -- | -- | 4.54 | -- | 14 | 11.3 | -- | -- | 4.81 | 15 | -- | 5.24 | 4.61 | -- | 16 | 11.2 | -- | -- | 5.01 | 17 | -- | 4.57 | -- | -- | 18 | 11.0 | -- | 4.30 | -- | 19 | -- | 4.26 | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Film fairly | | |Sticky, end |firm, end of| | |1st day; |3d day. | | |tacky, end 2d | | | |day; slightly | | | |tacky, end | | | |10th day.

TABLE X.--(_b_) SUN FLOWER OIL 20 PER CENT.

RAW LINSEED OIL 80 PER CENT.

----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.1600 | 0.5030 | 0.4470 | 0.2261 Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 | 9.5 | 14.21 | 12.62 | 11.54 | 2 | 11.0 | 14.21 | 12.02 | 11.85 | 3 | 11.1 | 12.66 | 11.48 | 9.92 | 4 | 11.3 | 14.01 | 11.65 | 9.13 | 5 | 11.4 | 11.59 | 10.25 | 8.95 | 6 | 10.9 | -- | -- | 9.04 | 7 | -- | 10.24 | 8.14 | -- | 8 | 10.8 | 10.63 | -- | 9.52 | 9 | -- | 10.34 | 6.26 | -- Percentage | 10 | 10.8 | 10.34 | -- | 8.55 Increase | 11 | -- | -- | 5.54 | -- in Weight, | 12 | 10.8 | 10.27 | -- | 7.67 in Days. | 13 | -- | -- | 6.22 | -- | 14 | 10.6 | -- | -- | 8.20 | 15 | -- | 11.33 | 5.82 | -- | 16 | 10.6 | -- | -- | -- | 17 | -- | 10.73 | -- | -- | 18 | 10.9 | -- | 5.35 | -- | 19 | -- | 10.30 | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Good firm, | | |Dry on 1st, 2d |glossy film | | |and 10th days.

|shown at end| | | |of 2d day. | | | ----------------+------------+-----------+-----------+--------------

TABLE XI.--(_a_) MENHADEN OIL 100 PER CENT.

----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.1944 | 0.5282 | 0.7005 | 0.3150 Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 | 7.7 | 12.47 | 10.79 | 11.27 | 2 | 8.1 | 12.17 | 10.98 | 10.16 | 3 | 8.9 | 11.70 | 10.85 | 9.72 | 4 | 10.1 | 11.47 | 10.90 | 9.97 | 5 | 9.8 | 11.13 | 10.57 | 9.94 | 6 | 9.8 | -- | -- | 10.27 | 7 | -- | 10.28 | 9.27 | -- | 8 | 9.8 | 11.20 | -- | 10.36 | 9 | -- | 11.15 | 8.48 | -- Percentage | 10 | 9.8 | 11.02 | -- | 8.80 Increase | 11 | -- | -- | 8.27 | -- in Weight, | 12 | 9.8 | 11.37 | -- | 9.22 in Days. | 13 | -- | -- | 8.91 | -- | 14 | 9.6 | -- | -- | 9.40 | 15 | -- | 10.85 | 8.75 | -- | 16 | 9.6 | -- | -- | 9.31 | 17 | -- | 10.34 | -- | -- | 18 | 9.6 | -- | 9.21 | -- | 19 | -- | 9.90 | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Good drying | | |Sticky, end |during 2d | | |1st day.

|day. Fairly | | |Slightly |firm film. | | |sticky, end 2d | | | |and 10th days.

(_b_) MENHADEN OIL 20 PER CENT.

RAW LINSEED OIL 80 PER CENT.

----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.2448 | 0.4959 | 0.4201 | 0.2456 Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 | 8.5 | 14.11 | 13.19 | 10.99 | 2 | 10.4 | 13.47 | 12.88 | 11.28 | 3 | 12.2 | 12.68 | 12.23 | 9.56 | 4 | 12.9 | 12.04 | 11.81 | 8.90 | 5 | 12.9 | 11.59 | 11.17 | 8.72 | 6 | 12.9 | -- | -- | 8.72 | 7 | -- | 10.44 | 9.50 | -- | 8 | 12.9 | 11.09 | -- | 9.34 | 9 | -- | 11.04 | 8.48 | -- Percentage | 10 | 12.9 | 10.74 | -- | 8.40 Increase | 11 | -- | -- | 7.77 | -- in Weight, | 12 | 12.9 | 10.90 | -- | 7.37 in Days. | 13 | -- | -- | 8.33 | -- | 14 | 12.8 | -- | -- | 8.11 | 15 | -- | 10.18 | 8.24 | -- | 16 | 12.7 | -- | -- | -- | 17 | -- | 9.48 | -- | -- | 18 | 12.9 | -- | 8.12 | -- | 19 | -- | 8.93 | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Good firm, | | |Nearly dry on |elastic film| | |1st and 2d |shown after | | |days.

|2d day. | | | ----------------+------------+-----------+-----------+--------------

TABLE XII.--(_a_) RAW CHINESE WOOD OIL 100 PER CENT.

----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.2266 | 0.5545 | 0.4933 | 0.4036 Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 | 4.1 | -- | 0.59 | 0.54 | 2 | 11.2 | -- | 2.09 | 2.80 | 3 | 14.9 | 11.02 | 5.13 | 5.10 | 4 | 14.4 | 11.53 | 7.56 | 6.00 | 5 | 14.4 | 11.03 | 8.68 | 6.27 | 6 | 14.2 | -- | -- | 7.09 | 7 | -- | 10.53 | 10.11 | -- | 8 | 14.2 | 10.74 | -- | 8.39 | 9 | -- | 10.47 | 9.65 | -- Percentage | 10 | 14.2 | 10.27 | -- | 8.01 Increase | 11 | -- | -- | 9.43 | -- in Weight, | 12 | 14.2 | 10.22 | -- | 8.55 in Days. | 13 | -- | -- | 9.77 | -- | 14 | 14.2 | -- | -- | 9.13 | 15 | -- | 9.80 | 9.73 | -- | 16 | 14.2 | -- | -- | 9.27 | 17 | -- | 9.25 | -- | -- | 18 | 14.5 | -- | 9.33 | -- | 19 | -- | 8.86 | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Film crys- | | |Sticky, end of |tallized and| | |1st and 2d |remained | | |days; dry but |soft until | | |drawn, end of |3d day. Hard| | |10th day.

|but opaque | | | |film shown | | | |after 4th | | | |day. | | | ----------------+------------+-----------+-----------+--------------

(_b_) RAW CHINESE WOOD OIL 20 PER CENT.

RAW LINSEED OIL 80 PER CENT.

----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.2087 | 0.2967 | 0.3683 | 0.2285 Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 | 9.0 | 14.46 | 14.37 | 11.99 | 2 | 12.1 | 13.11 | 13.66 | 11.90 | 3 | 12.9 | 11.72 | 13.11 | 10.14 | 4 | 12.8 | 10.68 | 12.41 | 9.30 | 5 | 12.8 | 9.77 | 11.78 | 9.08 | 6 | 12.8 | -- | -- | 9.30 | 7 | -- | 8.66 | 10.51 | -- | 8 | 12.7 | 8.86 | -- | 9.70 | 9 | -- | 8.80 | 8.72 | -- Percentage | 10 | 12.6 | 8.49 | -- | 8.90 Increase | 11 | -- | -- | 7.0 | -- in Weight, | 12 | 12.6 | 8.15 | -- | 7.34 in Days. | 13 | -- | -- | 8.82 | -- | 14 | 12.5 | -- | -- | 7.78 | 15 | -- | 8.05 | 8.39 | -- | 16 | 12.5 | -- | -- | -- | 17 | -- | 7.41 | -- | -- | 18 | 12.7 | -- | 7.98 | -- | 19 | -- | 7.04 | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Clear and | | |Dry at end of |firm film | | |1st day.

|shown after | | | |3d day. | | | ----------------+------------+-----------+-----------+--------------

TABLE XIII.--(_a_) CHINESE WOOD OIL (TREATED) 100 PER CENT.

----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.1678 | 0.4159 | 0.2934 | 0.3937 Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 |[13]38.0 |[13]19.06 |[13]0.92 | 3.53 | 2 |[13]30.0 |[13]20.16 |[13]0.41 | 3.58 | 3 |[13]28.0 |[13]20.47 | 0.72 | 3.25 | 4 |[13]28.0 |[13]20.47 | 0.79 | 3.25 | 5 |[13]28.0 |[13]20.80 | 0.13 | 3.33 | 6 |[13]28.0 | -- | -- | 2.93 | 7 | -- |[13]21.09 | 0.22 | -- | 8 |[13]28.0 |[13]20.87 | -- | 2.55 | 9 | -- |[13]20.98 | 0.46 | -- Percentage | 10 | 27.5 |[13]20.78 | -- | 3.40 Increase | 11 | -- | -- | 0.44 | -- in Weight, | 12 |[13]26.0 |[13]20.70 | -- | 3.23 in Days. | 13 | -- | -- | 0.43 | -- | 14 |[13]26.0 | -- | -- | 2.61 | 15 | -- |[13]20.97 | 0.42 | -- | 16 |[13]26.0 | -- | -- | 2.48 | 17 | -- |[13]21.22 | -- | -- | 18 |[13]26.2 | -- | 0.43 | -- | 19 | -- |[13]21.11 | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Loss ob- | | |Dry at end of |served due | | |1st day.

|to presence | | | |of vola- | | | |tiles. Firm,| | | |clear film | | | |shown at end| | | |of 1st day. | | | ----------------+------------+-----------+-----------+--------------

[13] Lost in weight throughout test.

TABLE XIII.--(_b_) CHINESE WOOD OIL (TREATED) 20 PER CENT.

RAW LINSEED OIL 80 PER CENT.

----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.1638 | 0.6572 | 0.4892 | 0.2644 Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 | 8.4 | 9.25 | 8.93 | 3.21 | 2 | 9.4 | 8.07 | 8.71 | 3.48 | 3 | 9.8 | 7.36 | 8.44 | 2.15 | 4 | 9.7 | 6.75 | 8.16 | 1.58 | 5 | 9.9 | 6.25 | 7.95 | 1.56 | 6 | 9.9 | -- | -- | 1.77 | 7 | -- | 5.49 | 6.75 | -- | 8 | 10.0 | 5.87 | -- | 2.30 | 9 | -- | 5.70 | 5.99 | -- Percentage | 10 | 9.6 | 5.67 | -- | 1.62 Increase | 11 | -- | -- | 5.50 | -- in Weight, | 12 | 9.5 | 4.37 | -- | 0.86 in Days. | 13 | -- | -- | 6.40 | -- | 14 | 9.5 | -- | -- | 1.50 | 15 | -- | 5.15 | 6.01 | -- | 16 | 9.5 | -- | -- | -- | 17 | -- | 4.69 | -- | -- | 18 | 9.6 | -- | 5.87 | -- | 19 | -- | 4.17 | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Clear and | | |Dry at end of |hard film | | |1st day.

|shown during| | | |2d day. | | | ----------------+------------+-----------+-----------+---------------

TABLE XIV.--(_a_) 20 PER CENT. DRY ROSIN IN 80 PER CENT. LINSEED OIL 100 PER CENT.

----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.2030 | -- | 0.5185 | 0.2554 Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 | 12.0 | -- | 3.76 | 1.80 | 2 | 14.1 | -- | 8.76 | 11.78 | 3 | 14.8 | -- | 9.20 | 12.17 | 4 | 14.2 | -- | 9.20 | 12.29 | 5 | 14.5 | -- | 8.49 | 12.02 | 6 | 14.0 | -- | -- | 12.49 | 7 | -- | -- | 9.07 | -- | 8 | 14.1 | -- | -- | 13.15 | 9 | -- | -- | 9.01 | -- Percentage | 10 | 14.1 | -- | -- | 11.85 Increase | 11 | -- | -- | 9.09 | -- in Weight, | 12 | 14.0 | -- | -- | 11.78 in Days. | 13 | -- | -- | 10.50 | -- | 14 | 14.0 | -- | -- | 12.69 | 15 | -- | -- | 10.16 | -- | 16 | 14.0 | -- | -- | 12.83 | 17 | -- | -- | -- | -- | 18 | 14.1 | -- | 10.18 | -- | 19 | -- | -- | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Rapid drying| | |Oily, end 1st |observed. | | |and 2d days; |Hard film | | |slightly |shown during| | |tacky, end |2d day. | | |10th day.

(_b_) 20 PER CENT. DRY ROSIN IN 80 PER CENT. LINSEED OIL 20 PER CENT.

RAW LINSEED OIL 80 PER CENT.

----------------+------------+-----------+-----------+-------------- Observer. | Gardner | Sabin | Pickard | { Rogers } | | | | { North } ----------------+------------+-----------+-----------+-------------- Wt. of Oil for | 0.1500 | 0.7105 | 0.4568 | -- Test, grams | | | | -----------+----+------------+-----------+-----------+-------------- | 1 | 10.9 | 14.19 | 12.86 | -- | 2 | 13.5 | 13.17 | 12.73 | -- | 3 | 13.6 | 11.84 | 12.13 | -- | 4 | 13.0 | 11.46 | 12.02 | -- | 5 | 13.0 | 10.87 | 11.30 | -- | 6 | 13.0 | -- | -- | -- | 7 | -- | 9.80 | 10.95 | -- | 8 | 13.1 | 10.33 | -- | -- | 9 | -- | 10.40 | 11.21 | -- Percentage | 10 | 13.1 | 10.04 | -- | -- Increase | 11 | -- | -- | 10.53 | -- in Weight, | 12 | 13.0 | 10.35 | -- | -- in Days. | 13 | -- | -- | 11.21 | -- | 14 | 12.9 | -- | -- | -- | 15 | -- | 9.64 | 10.88 | -- | 16 | 13.0 | -- | -- | -- | 17 | -- | 8.98 | -- | -- | 18 | 13.2 | -- | 11.43 | -- | 19 | -- | 8.62 | -- | -- -----------+----+------------+-----------+-----------+-------------- Remarks. |Clear, hard | | | |film after | | | |2d day. | | | ----------------+------------+-----------+-----------+--------------

TABLE XV.--(_a_) RAW LINSEED OIL 100 PER CENT.[14]

----------------+-----------+----------- Observer. | Sabin | Pickard | | ----------------+-----------+----------- Wt. of Oil for | 0.5274 | 0.5326 Test, grams | | -----------+----+-----------+----------- | 1 | 0.26 | 12.42 | 2 | 0.51 | 12.39 | 3 | 0.11 | 11.88 | 4 | 2.35 | 11.83 | 5 | 9.14 | 11.08 | 6 | -- | -- | 7 | 14.48 | 10.29 | 8 | 14.48 | -- | 9 | 14.18 | 9.56 Percentage | 10 | 13.86 | -- Increase | 11 | -- | 9.85 in Weight, | 12 | 13.00 | -- in Days. | 13 | -- | 10.30 | 14 | -- | -- | 15 | 12.23 | 10.12 | 16 | -- | -- | 17 | 11.66 | -- | 18 | -- | 10.78 | 19 | 11.07 | -- -----------+----+-----------+----------- Remarks. | | ----------------+-----------+-----------

[14] The test of this oil was made without the addition of 5 per cent.

of drier, the quant.i.ty used in all the other tests.

(_b_) DRIER 100 PER CENT.

----------------+-------------- Observer. | { Rogers } | { North } ----------------+-------------- Wt. of Oil for | 0.3445 Test, grams | -----------+----+-------------- | 1 | 48.95 | 2 | 48.53 | 3 | 48.68 | 4 | 48.68 | 5 | 48.48 | 6 | 48.26 | 7 | -- | 8 | 48.43 | 9 | -- Percentage | 10 | 48.89 Increase | 11 | -- in Weight, | 12 | 48.22 in Days. | 13 | -- | 14 | 48.22 | 15 | -- | 16 | -- | 17 | -- | 18 | -- | 19 | -- -----------+----+-------------- Remarks. | Dry at end of | 1st day.

CHAPTER III

PAINT PIGMENTS AND THEIR PROPERTIES

For the student of paint technology, who is not already acquainted with the chemistry and physics of the various raw pigments which are largely used in the manufacture of paints, the writer advises a careful reading of this chapter, in which the matter has been condensed as much as possible. In order to more thoroughly acquaint the reader with the physical const.i.tution of the pigments under consideration, there has been included photomicrographs, which show to advantage the structure of each.[15]

[15] The author gratefully acknowledges the a.s.sistance of Dr. J. A.

Schaeffer in the preparation of the photomicrographs shown in this chapter.

[Ill.u.s.tration: By Polarized Light

By Transmitted Light

Basic Carbonate-White Lead]

=Basic Carbonate-White Lead.= This pigment is made by stacking clay pots containing dilute acetic acid and lead buckles, in tiers, and covering them with tan bark. Fermentation of the tan bark, with subsequent formation of carbon dioxide acting on the acetate of lead formed within the pots, produces basic carbonate of lead. After complete corrosion, the white lead is ground, floated, and dried. Corroded white lead has a specific gravity of 6.8 and contains about 85% lead oxide and 15% of carbon dioxide and water. Its opaque nature and excellent body renders it extremely valuable as a const.i.tuent of paints. Checking and chalking progress rapidly when the pigment is used alone. The various sized particles, both large and small, resulting from the corrosion process, are prominently shown in the photomicrograph.

[Ill.u.s.tration: Crystals of Cerussite in Old Dutch Process White Lead.