"I will get some chairs," said Johnny, disappearing as soon as the guests were ushered in; while Sue politely offered the chair to Belle.
"Johnny don't have company in the laboratory very often," she explained.
Johnny came back immediately, bringing two chairs; but Alec said he did not care to sit down at present. As for Johnny, he was very busy taking things from the closet-shelf, and arranging them on the table, talking all the time.
"I suppose you know what chemical union is?" said Johnny to Alec.
"No, I don't think I do," replied Alec hesitatingly. "That is, although I know what union means, and what chemical means, I am not sure what they mean together."
"You know how sugar and salt dissolve in water, the particles of sugar and salt lying between the particles of water, just as a whole lot of different kinds of little seeds might be all mixed together without uniting at all?"
"I never thought about that before," replied Alec. "I didn't suppose fluid could be compared to seeds; and I had an idea that the salt and sugar became fluid somehow when they were dissolved, and so mixed in with the water."
"The particles of the water are very small; and the sugar and salt, when they come into contact with water, separate into very tiny particles, which fill in the places between the particles of water until there is no room left, and then all the sugar or salt you put in afterwards settles to the bottom by itself. But there is no union at all between the salt or sugar and the water; that is, they do not unite to form any different substance."
While Johnny was saying this, he was pouring some grayish powder into a cup. Then he put an old spoon in the powder, and took a vial of yellow liquid from the shelf.
"This is whiting," said Johnny. "If I put some water on it, and stir them together, I shall have nothing but whiting and water. Perhaps I'd better prove that first."