I2c problem

Hello,
I'd like to ask a little bit help.
I downloaded the mcb517_i2c aplication note.
I try to read the LM75 tempereture sensor with the bit_bang i2c routines.
The problem is...
There is a 16 bit temperature register and I can read only the high byte .
I use the following program
.
.
unsigned char data_in;
i2c_start();
i2c_write(0x91);
data_in=i2c_read();
i2c_stop();

I try to use the unsigned int instead unsigned char and modified the i2c_read routin to read 16 bit but no succes.

Any advice?
Cheer George