Peat or moss has been used in many cases with the best results, whilst with some waters potatoes act well. The residue in the boiler is soft, and the blowcock should be frequently used. Many other organic materials have from time to time been in the market. They form an important class of substances, and many of them give good results. The analyses of the incrustations show an increase in the proportion of organic matter, but otherwise they do not materially differ from those obtained from the same waters when no anti-in-crustator is used.

These organic substances are frequently mixed with salts, and have then the properties of both classes - that is to say, chemical and mechanical actions. They are liable, however, when used with hard waters, to form somewhat dense cakes, which become more or less hard, are charred, and cause overheating and consequent damage. This seems to be due to an excess of the saline constituent, for natural substances containing little alkaline base in proportion to organic constituent do not seem to give similar results, rhe saline ingredient is generally caustic soda or soda ash.

In this class ranks Baudet's patent, which consists in adding to the water sodic thiosulphate dissolved in rain water, and mixed with glycerine. The advantages claimed by the patentee are a greater solubility tor the calcic sulphate, whilst the phosphates and carbonates are precipitated and form a gelatinous mass with the glycerine. To the same series must also be added Bonneville's patent, which consists of baric carbonate, ammonic nitrate, common salt, and vegetable charcoal, a mixture which has the double advantages of being complex and somewhat costly

with comparison to others of the same series. Substances containing tannin are not unfrequent, but as they are generally presented in a dry form, should be well soaked in water before being introduced into the boiler, else they are liable to be carried over mechanically with the steam, and give much annoyance by choking the pipes and valves. Care must be taken also where the steam is to be blown into tanks for heating purposes, as in flax and hemp boiling, the tannic acid form -ing with the iron present in the fibre a black stain or blot, which cannot be bleached without the use of an acid, and consequent liability to damage the tissue. Table Q gives the results of the analysis of a portion of scum obtained from a flax boiler, and it will be seen that the iron is present in considerable quantity.

Table 0. - Boiler Incrustations. - Organic Composition Used

Pits.

Well.

Pits.

Pits.

Pits.

Ferric Oxide (Fe203) .. ..

1 2.20

2 60

2 64

308

14.00

5.16

1.68

Aluminic Oxide (A1203)

Calcic Carbonate (CaC03) ..

29.28

10 18

16.54

44.32

19.84

16.00

29-69

Magnesic Carbonate (MgC03)

611

7.46

22.84

20 76

16.44

25.60

37.32

Calcic Sulphate (CaSO4) ..

53.53

71 35

28 08

11.16

30. 03

18.28

22.32

Sodic Salts,etc........

0 54

0 32

123

0.41

0.36

0.92

1.3

Silica(SiO2)...........

2.29

2 22

812

14 46

12. 22

19.43

384

Organic Matter.....

3.37

4.14

14.04

2 26

8.03

11.13

2.65

Moisture.............

2.32

1.74

6.58

3.53

1.74

3.42

0.98

Total .. ..

99 64

100 01

100.07

99 98

99.76

99.94

99.79

Table P. - Boiler Incrustations. - Mixed Organic And Saline Composition Used

-

Spring, Surface and Well.

Sewage and Surface.

Sewage and Surface.

Canal.

Sewage, Born.

Sewage.

Loch.

Canal.

Sewage.

Ferric Oxide (Fe2O3) ..

5.36

2.12

4.16

1.96

3.84

3.68

3.72

4.16

4.72

5.20

Aluminic Oxide (Al2O3)

Calcic Carbonate (CaCO3) ..

71.67

8.68

15.17

11.36

8.28

47.35

58.78

60.85

69.55

27.06

Magnesic Carbonate (MgC03)

11.08

15*40

11.08

7.76

13 96

6.42

6.84

19.44

11.92

10.88

Calcic Sulphate (CaS04)

8.56

59 60

55.96

66.16

65.48

33.10

16.24

6.33

4.80

36.16

Sodic Salts,etc...

0*62

3.14

4.46

6.67

0.66

0 36

3.11

1.17

1.22

0*14

Silica........

1.24

3*65

730

2.24

6 23

6.43

6.61

.*56

5.24

15.88

Organic Matter.........

0.86

0 86

2*23

2 37

0.86

0.58

1.60

0.26

0.31

2.06

Moisture................

0.49

6.33

1.59

1.35

1.22

1.84

2.97

2.08

2.27

2.72

Total .. ..

99.88

99.78

99.95

99.87

100.43

99 76

99 97

99.88

100.03

100-10

Zinc has been employed in some cases, but has not been successful in boilers fed with fresh water, although with sea water it is said to be of use. The action seems to be one in which the zinc becomes a chloride. It is said that steamers whose boilers required at one time very frequent "chipping out" can now run considerable distances, with the frequent use of the blowcock.

Mechanical apparatus placed inside boilers has not proved successful, and electricity has given like results. The eoatiug of boilers with copper is injurious, and zinc galvanizing is dissolved rapidly even with a fresh-water supply.

Table Q. - Analysis Of Scum From Flax Boiler In Which An Anti-Incrustator Containing Tannin Was Used

Moisture ......

32.52

Organic Vegetable Matter

20.44

Ferric Oxide

4.56

Calcic Carbonate ..

18.04

Magnesia and Magnesic

Carbonate..

8.34

Potash Salts..

2.12

Silicious Matter ..

13.98

Total Saline Matter •

47.04

100.00

Looking at the great loss of heat consequent on the formation of scale, it seems astonishing that so little has been done in softening water for steam raising. The loss of heat, in many cases, is enormous. George . Davis mentions one instance where 17 per cent, of the whole disappeared, and this figure, large as it was, is much below the maximum loss. This loss of heat will be more readily appreciated when it is stated that 1/6 in. of scale represents the employment of 16 per cent, more fuel; 1/4-in. scale equals 50 per cent, extra coal, and a 1/2-inch deposit means 150 per cent, of additional firing. Many engineers believe in the necessity of a certain amount of scale to tighten the joints and rivet heads, but it is an indisputable fact that the cleaner the plates the less the loss in fuel. When the water contains calcic carbonate in solution, heating it will generally suffice, and for this purpose mechanical heaters are useful. One ingenious patent consists in a small tank placed in the boiler (an egg end), with the exit tube taken from near the top.

The apparatus is said to work well, but it is useless when calcic sulphate is present in the water, as that body does not become insoluble till heated under pressure to about 302° F. (150° C). The following analysis will illustrate the action of these mechanical heaters. The boilers to be fed are multitubular, and much difficulty is experienced from deposit, the available water being hard in quality, and having much matter in suspension. This suspended matter varies considerably throughout the day.

Table R. - Mechanical Heaters. Boiler Supply. In 1 Imp. Gal

Water before the

Heaters.

Water after

Heaters.

Saline Matter ..

28.42

28.68

Organic Matter ..

1.56

0.94

Total Solid Mattel

29.98

29.62

Suspended Matter:-

Gr.

Gr.

Principally Organic

0.46

-

Precipitated Carbonate of Calcium

-

2.48

In Solution:-

Calcic Carbonate..

6.64

4.48

Calcic Sulphate ..

8.24

8.06

From these results it is seen that the calcic carbonate suspended in the water can be traced to the loss of calcic carbonate in solution. Little good, however, has been done, as the suspended matter is not taken out of the water before it passes to the boilers. After some improvement in the heaters, another analysis of the water gave better results.

Table S. - Mechanical Heaters. Boiler Supply

In 1 Imp. Gal.:-

Gr.

Sline Matter...

15.84

Organic Matter..

0.85

Total Solid Matter

.. 16.72

In Suspension:-

Calcic Carbonate ..

0.46

In Solution:-

Calcic Carbonate..

1.24

Calcic Sulphate..

2.44

Soda Salts........

..Abundant

It now appears that the calcic carbonate has decreased very much. This result-was obtained by an increase of temperature consequent on the employment of steam direct from the boilers, in place of the waste steam from the cylinder, as previously utilized. At the same time sodic carbonate was introduced along with the feed water, which, acting on the calcic sulphate, caused double decomposition, with precipitation of calcic carbonate. The following analysis of the scale from the boilers before and after the employment of the heaters is interesting: -