— | Ash, per cent. on Dried Skin | |
Time of Puering in | Washed Delimed | Limed Roan (B) |
0 | 2·88 | 7·03 |
5 | 2·91 | — |
10 | 3·20 | 3·54 |
15 | 4·80 | — |
20 | 4·08 | 4·24 |
25 | 4·29 | — |
30 | 4·85 | 5·19 |
35 | 4·59 | — |
40 | 4·70 | 5·45 |
45 | 4·60 | — |
50 | 4·45 | 5·67 |
55 | 4·42 | — |
60 | — | 5·00 |
The following analyses give the amount of lime in solution before and after the bating of the skins, in grams per litre of filtered puer liquor:—
| No. | Bate | Before Goods | After Goods | Increase of CaO |
| 1 | Fresh puer | 0·108 | 0·62 | 0·512 |
| 2 | " " | 0·34 | 0·72 | 0·38 |
| 3 | " " | 0·20 | 0·52 | 0·32 |
| 4 | " " | 0·19 | 0·49 | 0·30 |
| 5 | Old puer | 0·54 | 0·84 | 0·30 |
| 6 | Old puer, goods not washed. | 0·98 | 1·38 | 0·40 |
| 7 | French puer shop. | 0·308 | 0·548 | 0·24 |
The limit of the quantity of lime in solution in a normal puer, in the form of calcium salts, appears to be about 1 grm. per litre. If more lime be presented to the liquor, the goods stop coming down. If now fresh dung be added, they will continue to come down, but the quantity of lime in solution does not increase; the excess of lime is precipitated, partly as phosphate and partly as oxalate, in the way stated above.
The type of reaction by which the lime is dissolved is similar to that occurring between ammonium chloride and lime, and is expressed by the formula—
2NH4Cl + Ca(OH)2 = CaCl2 + 2NH3 + 2H2O
and in the case of the calcium carbonate in the skins—
2NH4Cl + CaCO3 = CaCl2 + (NH4)2CO3,
so that every molecule of lime neutralized, liberates two molecules of ammonia.