Soft water, especially when full of air, or when containing organic matter, acts upon lead in such a way that some of it is taken up in solution, and the water is poisoned.

This makes lead a dangerous material to use in many cases for cisterns and pipes connected with the supply of water for drinking purposes, or for roofs and flats whence that supply may be drawn.

Vitiated or impure air acts upon lead in a somewhat similar manner.

There has been a good deal of discussion with regard to the action of different kinds of water upon lead, as the subject is an important one, the following remarks are inserted. They are chiefly founded upon the valuable standard work on hygiene by the late Professor Parkes.

Pure water, not containing air, does not act upon pure lead.

When the water contains much oxygen, the lead is oxidised; and oxide of lead, a highly poisonous substance, is to some extent soluble in water.

If there is much carbonic acid present it converts some of the oxide into carbonate of lead, which is almost insoluble and therefore comparatively harmless.

The waters which act most upon lead are the purest and most highly oxygenated, also those containing organic matter - nitrites, nitrates, and chlorides.

The waters which act least upon lead are those containing carbonate of lime and jihosphate of lime, in a less degree sulphate of lime. Some of these form a coating on the inside of the pipe which protects it from further action.

Some vegetable substances contained in water, peaty matter for example, also protect the pipe by forming an internal coating upon it.

It appears therefore that hard waters, containing (as they generally do) carbonate of lime, do not readily affect lead.

Soft waters, such as rain water, and water obtaiued by distillation - water polluted with sewage - water in tanks having a muddy deposit - may all become poisoned when in contact with lead.

"The mud of several rivers, even the Thames, will corrode lead, probably from the organic matter it contains, but it does not necessarily follow that any lead has been dissolved in the water. Bits of mortar will also corrode lead." 1

Vegetables and fatty acids arising from fruit and vegetables, cider, sour milk, etc., also act upon lead.

The poisonous effects of lead show themselves in other materials connected with building.

For example, white lead, the basis of most paints, is a highly poisonous substance, and leads to serious diseases among the workmen who manufacture the white lead, and among the painters who use it (see p. 406).

Lead Pipes are much used in connection with water supply, etc.

Pipes of large diameter are generally made by the plumber out of sheet lead.

Smaller pipes used to be cast in short lengths of considerable thickness, and then drawn out to the proper dimensions.

Now, however, they are generally formed by forcing the molten metal, by hydraulic pressure, through a die of the section required.

Soil pipes should always be "drawn," and are thus made of from 31/2 to 5 inches diameter, and of thicknesses equal to those, of sheet lead varying in weight from 5 to 10 lbs. per square foot.

Water pipes. - The thickness and consequently the weight of lead pipes used for water supply should be regulated by the pressure of water they are intended to bear.

1 Parkes' Hygiene.

The following Table shows the sizes and weights per yard run of pipes usually made and the heads of water to which they can be safely subjected in practice : -

Lengths in which made

Feet.

Internal diameter of pipe in inches.

Overflows.

Heads about 50 feet.

Heads about 300 feet.

Heads about 500 feet.

Weight in lbs. per yard run.

15

or in coils of 60 ft.

1/4

..

...

..

...

...

...

..

3.9

,,

3/8

...

...

...

...

3.

3.9

4.8

,,

1/2

27

3.

3.6

3.9

4.5

4.8

5.7

6.0

,,

5/8

...

...

...

...

3.6

4.5

6.0

,,

3/4

4.5

4.8

51

5.7

6.3

7.2

8.4

9.0

,,

1

..

6

7.2

5.1

9.6

11.1

12.0

12.9

12

or in coils of from 40 to 50 ft.

11/4

..

..

...

9.0

10.5

12.0

12.9

15.0

,,

11/2

..

..

9.0

12.0

141

18.0

21.0

24.0

13/4

..

...

...

18.0

21.0

24.0

,,

2

...

9.0

14.1

18.0

21.0

24.0

27.9

30..

10

21/2

..

..

10.8

21.0

25.2

28.8

33.6

36.0

,,

3

12.6

18.0

24.0

30.0

33.6

36.0

39.0

42.0

,,

31/2

16.8

27.0

33..6

36.0

39..0

45.0

48.0

54.0

,,

4

16.8

21.0

24.0

33.6

420

48.0

51.0

60.0

,,

41/2

19.8

25.2

33.6

42.0

51.0

60.0

66.0

99

5

..

..

...

51.0

60.0

70.2

76.2

84.0

Number of Column

1

2

3

4

5

6

7

8

The above are reduced from the price list of Messrs. John Bolding and Sons, manufacturers.

Coating- Lead Pipes to prevent Poisoning. - Several methods have been proposed for coating and lining the insides of lead pipes to prevent the water conveyed by them from being poisoned.

All of these are condemned by Professor Parkes as being objectionable, except the following : -

M'Dougal's Patent consists in applying an internal bituminous coating, which is said to have been successful.

Schwartz's Patent

The pipe is boiled in sulphide of soda for fifteen minutes, by which the interior is coated with sulphide of lead (a substance insoluble in water).